CVE-2026-71513 (GCVE-0-2026-71513)

Vulnerability from cvelistv5 – Published: 2026-08-22 13:34 – Updated: 2026-08-27 16:24
VLAI
Title
NLTK 3.10.0 through 3.10.2 Remote Code Execution via AllowlistUnpickler Dotted-Name Bypass
Summary
NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load.
Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
8.8 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-25 03:56 UTC
CWE
  • CWE-502 - Deserialization of Untrusted Data
Assigner
References
Impacted products
Vendor Product Version
nltk nltk Affected: 3.10.0 , < 3.10.3 (semver)
Unaffected: 3.10.3 (semver)
    cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*
Create a notification for this product.
Date Public
2026-08-11 00:00
Credits
Tohirov Fazliddin Mahmud o'g'li
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-71513",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-25T03:56:57.129387Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-27T16:24:50.539Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:pypi/nltk",
          "product": "nltk",
          "vendor": "nltk",
          "versions": [
            {
              "lessThan": "3.10.3",
              "status": "affected",
              "version": "3.10.0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "3.10.3",
              "versionType": "semver"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "3.10.3",
                  "versionStartIncluding": "3.10.0",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Tohirov Fazliddin Mahmud o\u0027g\u0027li"
        }
      ],
      "datePublic": "2026-08-11T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 8.7,
            "baseSeverity": "HIGH",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "PASSIVE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "HIGH",
            "vulnIntegrityImpact": "HIGH"
          },
          "format": "CVSS"
        },
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-502",
              "description": "Deserialization of Untrusted Data",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-22T13:34:07.811Z",
        "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "shortName": "VulnCheck"
      },
      "references": [
        {
          "name": "Patch Commit",
          "tags": [
            "patch"
          ],
          "url": "https://github.com/nltk/nltk/commit/c3e37113742a1ebeeb4f2ca58941f320f98805ea"
        },
        {
          "tags": [
            "product"
          ],
          "url": "https://github.com/nltk/nltk"
        },
        {
          "tags": [
            "technical-description"
          ],
          "url": "https://github.com/nltk/nltk/blob/v3.10.2/nltk/picklesec.py#L119-L124"
        },
        {
          "name": "VulnCheck Advisory: NLTK 3.10.0 through 3.10.2 Remote Code Execution via AllowlistUnpickler Dotted-Name Bypass",
          "tags": [
            "third-party-advisory"
          ],
          "url": "https://www.vulncheck.com/advisories/nltk-through-remote-code-execution-via-allowlistunpickler-dotted-name-bypass"
        }
      ],
      "title": "NLTK 3.10.0 through 3.10.2 Remote Code Execution via AllowlistUnpickler Dotted-Name Bypass",
      "x_generator": {
        "engine": "vulncheck-endgame"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
    "assignerShortName": "VulnCheck",
    "cveId": "CVE-2026-71513",
    "datePublished": "2026-08-22T13:34:07.811Z",
    "dateReserved": "2026-08-06T20:42:17.834Z",
    "dateUpdated": "2026-08-27T16:24:50.539Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-71513",
      "date": "2026-10-02",
      "epss": "0.01097",
      "percentile": "0.64405"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "unaffected",
                "packageURL": "pkg:pypi/nltk",
                "product": "nltk",
                "vendor": "nltk",
                "versions": [
                  {
                    "lessThan": "3.10.3",
                    "status": "affected",
                    "version": "3.10.0",
                    "versionType": "semver"
                  },
                  {
                    "status": "unaffected",
                    "version": "3.10.3",
                    "versionType": "semver"
                  }
                ]
              }
            ],
            "source": "disclosure@vulncheck.com"
          }
        ],
        "configurations": [
          {
            "nodes": [
              {
                "cpeMatch": [
                  {
                    "criteria": "cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "907206A4-3761-4899-9D77-F79C72F6229B",
                    "versionEndExcluding": "3.10.3",
                    "vulnerable": true
                  }
                ],
                "negate": false,
                "operator": "OR"
              }
            ]
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load."
          }
        ],
        "id": "CVE-2026-71513",
        "lastModified": "2026-09-16T13:19:34.203",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 8.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "REQUIRED",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 2.8,
              "impactScore": 5.9,
              "source": "disclosure@vulncheck.com",
              "type": "Secondary"
            }
          ],
          "cvssMetricV40": [
            {
              "cvssData": {
                "Automatable": "NOT_DEFINED",
                "Recovery": "NOT_DEFINED",
                "Safety": "NOT_DEFINED",
                "attackComplexity": "LOW",
                "attackRequirements": "NONE",
                "attackVector": "NETWORK",
                "availabilityRequirement": "NOT_DEFINED",
                "baseScore": 8.7,
                "baseSeverity": "HIGH",
                "confidentialityRequirement": "NOT_DEFINED",
                "exploitMaturity": "NOT_DEFINED",
                "integrityRequirement": "NOT_DEFINED",
                "modifiedAttackComplexity": "NOT_DEFINED",
                "modifiedAttackRequirements": "NOT_DEFINED",
                "modifiedAttackVector": "NOT_DEFINED",
                "modifiedPrivilegesRequired": "NOT_DEFINED",
                "modifiedSubAvailabilityImpact": "NOT_DEFINED",
                "modifiedSubConfidentialityImpact": "NOT_DEFINED",
                "modifiedSubIntegrityImpact": "NOT_DEFINED",
                "modifiedUserInteraction": "NOT_DEFINED",
                "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
                "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
                "modifiedVulnIntegrityImpact": "NOT_DEFINED",
                "privilegesRequired": "NONE",
                "providerUrgency": "NOT_DEFINED",
                "subAvailabilityImpact": "NONE",
                "subConfidentialityImpact": "NONE",
                "subIntegrityImpact": "NONE",
                "userInteraction": "PASSIVE",
                "valueDensity": "NOT_DEFINED",
                "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
                "version": "4.0",
                "vulnAvailabilityImpact": "HIGH",
                "vulnConfidentialityImpact": "HIGH",
                "vulnIntegrityImpact": "HIGH",
                "vulnerabilityResponseEffort": "NOT_DEFINED"
              },
              "source": "disclosure@vulncheck.com",
              "type": "Secondary"
            }
          ],
          "ssvcV203": [
            {
              "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "ssvcData": {
                "id": "CVE-2026-71513",
                "options": [
                  {
                    "exploitation": "none"
                  },
                  {
                    "automatable": "no"
                  },
                  {
                    "technicalImpact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-25T03:56:57.129387Z",
                "version": "2.0.3"
              }
            }
          ]
        },
        "published": "2026-08-22T14:16:33.417",
        "references": [
          {
            "source": "disclosure@vulncheck.com",
            "tags": [
              "Product"
            ],
            "url": "https://github.com/nltk/nltk"
          },
          {
            "source": "disclosure@vulncheck.com",
            "tags": [
              "Product"
            ],
            "url": "https://github.com/nltk/nltk/blob/v3.10.2/nltk/picklesec.py#L119-L124"
          },
          {
            "source": "disclosure@vulncheck.com",
            "tags": [
              "Patch"
            ],
            "url": "https://github.com/nltk/nltk/commit/c3e37113742a1ebeeb4f2ca58941f320f98805ea"
          },
          {
            "source": "disclosure@vulncheck.com",
            "tags": [
              "Third Party Advisory",
              "Patch"
            ],
            "url": "https://www.vulncheck.com/advisories/nltk-through-remote-code-execution-via-allowlistunpickler-dotted-name-bypass"
          }
        ],
        "sourceIdentifier": "disclosure@vulncheck.com",
        "vulnStatus": "Analyzed",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-502"
              }
            ],
            "source": "disclosure@vulncheck.com",
            "type": "Secondary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-08-31T09:07:08+00:00",
      "cve": "CVE-2026-71513",
      "id": "CVE-2026-71513",
      "initial_release_date": "2026-08-22T13:34:07.811000+00:00",
      "product_status:known_affected": "4",
      "product_status:known_not_affected": "11",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "nltk: NLTK: Remote Code Execution via AllowlistUnpickler dotted-name bypass",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-71513.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": {
        "adp": [
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2026-71513",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "total"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-08-25T03:56:57.129387Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-08-27T16:15:04.460Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unaffected",
              "packageURL": "pkg:pypi/nltk",
              "product": "nltk",
              "vendor": "nltk",
              "versions": [
                {
                  "lessThan": "3.10.3",
                  "status": "affected",
                  "version": "3.10.0",
                  "versionType": "semver"
                },
                {
                  "status": "unaffected",
                  "version": "3.10.3",
                  "versionType": "semver"
                }
              ]
            }
          ],
          "cpeApplicability": [
            {
              "nodes": [
                {
                  "cpeMatch": [
                    {
                      "criteria": "cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "3.10.3",
                      "versionStartIncluding": "3.10.0",
                      "vulnerable": true
                    }
                  ],
                  "negate": false,
                  "operator": "OR"
                }
              ]
            }
          ],
          "credits": [
            {
              "lang": "en",
              "type": "finder",
              "value": "Tohirov Fazliddin Mahmud o\u0027g\u0027li"
            }
          ],
          "datePublic": "2026-08-11T00:00:00.000Z",
          "descriptions": [
            {
              "lang": "en",
              "value": "NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load."
            }
          ],
          "metrics": [
            {
              "cvssV4_0": {
                "attackComplexity": "LOW",
                "attackRequirements": "NONE",
                "attackVector": "NETWORK",
                "baseScore": 8.7,
                "baseSeverity": "HIGH",
                "privilegesRequired": "NONE",
                "subAvailabilityImpact": "NONE",
                "subConfidentialityImpact": "NONE",
                "subIntegrityImpact": "NONE",
                "userInteraction": "PASSIVE",
                "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
                "version": "4.0",
                "vulnAvailabilityImpact": "HIGH",
                "vulnConfidentialityImpact": "HIGH",
                "vulnIntegrityImpact": "HIGH"
              },
              "format": "CVSS"
            },
            {
              "cvssV3_1": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 8.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "REQUIRED",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "format": "CVSS"
            }
          ],
          "problemTypes": [
            {
              "descriptions": [
                {
                  "cweId": "CWE-502",
                  "description": "Deserialization of Untrusted Data",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-08-22T13:34:07.811Z",
            "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
            "shortName": "VulnCheck"
          },
          "references": [
            {
              "name": "Patch Commit",
              "tags": [
                "patch"
              ],
              "url": "https://github.com/nltk/nltk/commit/c3e37113742a1ebeeb4f2ca58941f320f98805ea"
            },
            {
              "tags": [
                "product"
              ],
              "url": "https://github.com/nltk/nltk"
            },
            {
              "tags": [
                "technical-description"
              ],
              "url": "https://github.com/nltk/nltk/blob/v3.10.2/nltk/picklesec.py#L119-L124"
            },
            {
              "name": "VulnCheck Advisory: NLTK 3.10.0 through 3.10.2 Remote Code Execution via AllowlistUnpickler Dotted-Name Bypass",
              "tags": [
                "third-party-advisory"
              ],
              "url": "https://www.vulncheck.com/advisories/nltk-through-remote-code-execution-via-allowlistunpickler-dotted-name-bypass"
            }
          ],
          "title": "NLTK 3.10.0 through 3.10.2 Remote Code Execution via AllowlistUnpickler Dotted-Name Bypass",
          "x_generator": {
            "engine": "vulncheck-endgame"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "assignerShortName": "VulnCheck",
        "cveId": "CVE-2026-71513",
        "datePublished": "2026-08-22T13:34:07.811Z",
        "dateReserved": "2026-08-06T20:42:17.834Z",
        "dateUpdated": "2026-08-25T03:56:56.352Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.