Vulnerability-Lookup

CVE-2026-44722 (GCVE-0-2026-44722)

Vulnerability from cvelistv5 – Published: 2026-07-17 16:42 – Updated: 2026-07-17 17:25

Title

pyzipper: Encryption bypass for small files encrypted with pyzipper

Summary

pyzipper is a replacement for Python's zipfile that can read and write AES encrypted zip files. Prior to 0.4.0, a Python operator precedence bug in pyzipper/zipfile_aes.py caused the AE-2 format to never be automatically selected during encryption, causing encrypted entries to be written in AE-1 format and exposing the plaintext CRC32 checksum in the ZIP header and, for unseekable zip archives, in the datadescripter section, allowing an attacker who possesses the archive to brute-force candidate plaintexts for small or low-entropy files by comparing CRC32 values. This issue is fixed in version 0.4.0.

Severity

6.2 (Medium)


                        
                          CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-17 17:25 UTC

CWE

CWE-480 - Use of Incorrect Operator

Assigner

GitHub_M mitre root Scorecard

References

3 references

URL	Tags
https://github.com/danifus/pyzipper/security/advi…	x_refsource_CONFIRM
https://github.com/danifus/pyzipper/commit/93ce88…	x_refsource_MISC
https://github.com/danifus/pyzipper/releases/tag/v0.4.0	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
danifus	pyzipper	Affected: < 0.4.0

Show details on NVD website

JSON

To clipboard

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EUVD-2026-338535

European Vulnerability Database identifier assigned by ENISA

Reserved

2026-10-02 07:52

Assigner

ENISA

Alias of

a CVE record, shown under related vulnerabilities. This identifier carries no description, severity or references of its own: they belong to that CVE.

JSON

To clipboard

{
  "assigner": "ENISA",
  "date_reserved": "2026-10-02T07:52:58.968264+00:00",
  "id": "EUVD-2026-338535"
}

FKIE_CVE-2026-44722

Vulnerability from fkie_nvd - Published: 2026-07-17 17:17 - Updated: 2026-07-17 18:45

Severity

6.2 (Medium) - CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/danifus/pyzipper/commit/93ce88e7dfd1635443197dab3fb8d477cff579ae
	security-advisories@github.com	https://github.com/danifus/pyzipper/releases/tag/v0.4.0
	security-advisories@github.com	https://github.com/danifus/pyzipper/security/advisories/GHSA-crqm-m339-7m2p

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "pyzipper",
          "vendor": "danifus",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 0.4.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
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    {
      "lang": "en",
      "value": "pyzipper is a replacement for Python\u0027s zipfile that can read and write AES encrypted zip files. Prior to 0.4.0, a Python operator precedence bug in pyzipper/zipfile_aes.py caused the AE-2 format to never be automatically selected during encryption, causing encrypted entries to be written in AE-1 format and exposing the plaintext CRC32 checksum in the ZIP header and, for unseekable zip archives, in the datadescripter section, allowing an attacker who possesses the archive to brute-force candidate plaintexts for small or low-entropy files by comparing CRC32 values. This issue is fixed in version 0.4.0."
    }
  ],
  "id": "CVE-2026-44722",
  "lastModified": "2026-07-17T18:45:20.713",
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          "baseScore": 6.2,
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GHSA-CRQM-M339-7M2P

Vulnerability from github – Published: 2026-05-14 16:17 – Updated: 2026-05-14 16:17

Summary

pyzipper has an encryption bypass for small files encrypted using it

Details

Impact

A Python operator precedence bug in pyzipper/zipfile_aes.py caused the AE-2 format to never be automatically selected during encryption, regardless of file size or compression type. As a result, all encrypted entries are written in AE-1 format unless AE-2 is explicitly forced by the caller. AE-1 stores the plaintext CRC32 checksum unencrypted in the ZIP header. During investigation of this issue, it was also found that when writing to an unseekable zip archive, the CRC32 value was always written to the datadescripter section.

The AES encryption itself is not broken. An attacker who possesses the archive can read the CRC32 from the header without decrypting anything, then brute-force candidate plaintexts by computing CRC32(candidate) and comparing against the stored value. In practice, this attack is feasible today only against small or low-entropy files, as CRC32 exhaustion across a large plaintext space is computationally prohibitive on current hardware. Files with high-entropy or large content are not practically at risk under current computing constraints. Without this bug, pyzipper would have removed the CRC32 value for any file with content of less than 20 bytes uncompressed.

Patches

Upgrade to pyzipper 0.4.0 that changes the default behaviour of pyzipper to always use the AE-2 format and exclude the CRC32 values, unless instructed to do otherwise.

If rewriting the zip archive to remove the CRC values for small files, the entire zip archive should be recreated to avoid the original local file header with the CRC included remaining in the zip file in a detached state.

Credit

Thanks to Lucas Lavarello from Kulkan Security for identifying this issue.

References

https://www.winzip.com/en/support/aes-encryption/#CRC https://www.winzip.com/en/support/aes-encryption/#crc-faq

Severity

6.2 (Medium)


                  
                    CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "pyzipper"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.4.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-44722"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-480"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-14T16:17:01Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Impact\nA Python operator precedence bug in pyzipper/zipfile_aes.py caused the AE-2 format to never be automatically selected during encryption, regardless of file size or compression type. As a result, all encrypted entries are written in AE-1 format unless AE-2 is explicitly forced by the caller. AE-1 stores the plaintext CRC32 checksum unencrypted in the ZIP header. During investigation of this issue, it was also found that when writing to an unseekable zip archive, the CRC32 value was always written to the datadescripter section.\n\nThe AES encryption itself is not broken. An attacker who possesses the archive can read the CRC32 from the header without decrypting anything, then brute-force candidate plaintexts by computing CRC32(candidate) and comparing against the stored value. In practice, this attack is feasible today only against small or low-entropy files, as CRC32 exhaustion across a large plaintext space is computationally prohibitive on current hardware. Files with high-entropy or large content are not practically at risk under current computing constraints. Without this bug, pyzipper would have removed the CRC32 value for any file with content of less than 20 bytes uncompressed.\n\n### Patches\nUpgrade to pyzipper 0.4.0 that changes the default behaviour of pyzipper to always use the AE-2 format and exclude the CRC32 values, unless instructed to do otherwise.\n\nIf rewriting the zip archive to remove the CRC values for small files, the entire zip archive should be recreated to avoid the original local file header with the CRC included remaining in the zip file in a detached state.\n\n## Credit\nThanks to Lucas Lavarello from Kulkan Security for identifying this issue.\n\n### References\nhttps://www.winzip.com/en/support/aes-encryption/#CRC\nhttps://www.winzip.com/en/support/aes-encryption/#crc-faq",
  "id": "GHSA-crqm-m339-7m2p",
  "modified": "2026-05-14T16:17:01Z",
  "published": "2026-05-14T16:17:01Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/danifus/pyzipper/security/advisories/GHSA-crqm-m339-7m2p"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/danifus/pyzipper"
    },
    {
      "type": "WEB",
      "url": "https://github.com/danifus/pyzipper/releases/tag/v0.4.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "pyzipper has an encryption bypass for small files encrypted using it"
}

PYSEC-2026-3044

Vulnerability from pysec - Published: 2026-07-13 15:19 - Updated: 2026-07-13 16:06

Details

Impact

Patches

Upgrade to pyzipper 0.4.0 that changes the default behaviour of pyzipper to always use the AE-2 format and exclude the CRC32 values, unless instructed to do otherwise.

Credit

Thanks to Lucas Lavarello from Kulkan Security for identifying this issue.

References

https://www.winzip.com/en/support/aes-encryption/#CRC https://www.winzip.com/en/support/aes-encryption/#crc-faq

Severity

6.2 (Medium)


                  
                    CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Impacted products

Name	purl
pyzipper	pkg:pypi/pyzipper

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "pyzipper",
        "purl": "pkg:pypi/pyzipper"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.4.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.1.0",
        "0.2.0",
        "0.3.0",
        "0.3.1",
        "0.3.2",
        "0.3.3",
        "0.3.4",
        "0.3.5",
        "0.3.6"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-44722",
    "GHSA-crqm-m339-7m2p"
  ],
  "details": "### Impact\nA Python operator precedence bug in pyzipper/zipfile_aes.py caused the AE-2 format to never be automatically selected during encryption, regardless of file size or compression type. As a result, all encrypted entries are written in AE-1 format unless AE-2 is explicitly forced by the caller. AE-1 stores the plaintext CRC32 checksum unencrypted in the ZIP header. During investigation of this issue, it was also found that when writing to an unseekable zip archive, the CRC32 value was always written to the datadescripter section.\n\nThe AES encryption itself is not broken. An attacker who possesses the archive can read the CRC32 from the header without decrypting anything, then brute-force candidate plaintexts by computing CRC32(candidate) and comparing against the stored value. In practice, this attack is feasible today only against small or low-entropy files, as CRC32 exhaustion across a large plaintext space is computationally prohibitive on current hardware. Files with high-entropy or large content are not practically at risk under current computing constraints. Without this bug, pyzipper would have removed the CRC32 value for any file with content of less than 20 bytes uncompressed.\n\n### Patches\nUpgrade to pyzipper 0.4.0 that changes the default behaviour of pyzipper to always use the AE-2 format and exclude the CRC32 values, unless instructed to do otherwise.\n\nIf rewriting the zip archive to remove the CRC values for small files, the entire zip archive should be recreated to avoid the original local file header with the CRC included remaining in the zip file in a detached state.\n\n## Credit\nThanks to Lucas Lavarello from Kulkan Security for identifying this issue.\n\n### References\nhttps://www.winzip.com/en/support/aes-encryption/#CRC\nhttps://www.winzip.com/en/support/aes-encryption/#crc-faq",
  "id": "PYSEC-2026-3044",
  "modified": "2026-07-13T16:06:06.348133Z",
  "published": "2026-07-13T15:19:05.343307Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/danifus/pyzipper/security/advisories/GHSA-crqm-m339-7m2p"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/danifus/pyzipper"
    },
    {
      "type": "WEB",
      "url": "https://github.com/danifus/pyzipper/releases/tag/v0.4.0"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/pyzipper"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-crqm-m339-7m2p"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44722"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "pyzipper has an encryption bypass for small files encrypted using it"
}

UBUNTU-CVE-2026-44722 (CVE-2026-44722)

Vulnerability from osv_ubuntu – Published: 2026-07-17 17:17 – Updated: 2026-07-29 07:57 – Source website

Details

Severity

6.2 (Medium)


                    
                      CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-44722	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-44722	REPORT
	https://github.com/danifus/pyzipper/security/advi…	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "python3-pyzipper",
            "binary_version": "0.3.6-5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "python-pyzipper",
        "purl": "pkg:deb/ubuntu/python-pyzipper@0.3.6-5?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.3.6-5"
      ]
    }
  ],
  "aliases": [],
  "details": "pyzipper is a replacement for Python\u0027s zipfile that can read and write AES encrypted zip files. Prior to 0.4.0, a Python operator precedence bug in pyzipper/zipfile_aes.py caused the AE-2 format to never be automatically selected during encryption, causing encrypted entries to be written in AE-1 format and exposing the plaintext CRC32 checksum in the ZIP header and, for unseekable zip archives, in the datadescripter section, allowing an attacker who possesses the archive to brute-force candidate plaintexts for small or low-entropy files by comparing CRC32 values. This issue is fixed in version 0.4.0.",
  "id": "UBUNTU-CVE-2026-44722",
  "modified": "2026-07-29T07:57:02Z",
  "published": "2026-07-17T17:17:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-44722"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-44722"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/danifus/pyzipper/security/advisories/GHSA-crqm-m339-7m2p"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-44722"
  ]
}

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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.

Action not permitted

CVE-2026-44722 (GCVE-0-2026-44722)

EUVD-2026-338535

FKIE_CVE-2026-44722

GHSA-CRQM-M339-7M2P

Impact

Patches

Credit

References

PYSEC-2026-3044

Impact

Patches

Credit

References

UBUNTU-CVE-2026-44722 (CVE-2026-44722)

Tags

Sightings

Nomenclature

Related by attack behaviour