Vulnerability-Lookup

UBUNTU-CVE-2026-103399 (CVE-2026-103399)

Vulnerability from osv_ubuntu – Published: 2026-09-30 18:18 – Updated: 2026-10-08 09:54 – Source website

Details

A flaw was found in SoupServer (libsoup). When an HTTP/1.x client sends a request with Expect: 100-continue and a request body, and SoupServer returns an early final (non-1xx) response before the body is read, the server neither drains the declared body bytes nor closes the connection. On a keep-alive connection, those leftover bytes are interpreted as a subsequent HTTP request. A remote, unauthenticated attacker can place a complete HTTP request in the body and cause SoupServer to process that smuggled request, leading to unintended request handling.

Severity

5.3 (Medium)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-103399	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-103399	REPORT
	https://bugzilla.redhat.com/show_bug.cgi?id=2543949	REPORT
	https://gitlab.gnome.org/GNOME/libsoup/-/work_items/539	REPORT
	https://gitlab.gnome.org/GNOME/libsoup/-/merge_re…	REPORT
	https://access.redhat.com/security/cve/CVE-2026-103399	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "gir1.2-soup-2.4",
            "binary_version": "2.52.2-1ubuntu0.3+esm8"
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        "3.0.7-0ubuntu1+esm2",
        "3.0.7-0ubuntu1+esm3",
        "3.0.7-0ubuntu1+esm4",
        "3.0.7-0ubuntu1+esm5",
        "3.0.7-0ubuntu1+esm6",
        "3.0.7-0ubuntu1+esm7",
        "3.0.7-0ubuntu1+esm8",
        "3.0.7-0ubuntu1+esm9"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "gir1.2-soup-2.4",
            "binary_version": "2.74.3-6ubuntu1.9"
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          {
            "binary_name": "libsoup-2.4-1",
            "binary_version": "2.74.3-6ubuntu1.9"
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      },
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        "3.6.5-9",
        "3.6.6-1",
        "3.6.6-1ubuntu0.1"
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    },
    {
      "ecosystem_specific": {
        "binaries": [
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            "binary_name": "gir1.2-soup-2.4",
            "binary_version": "2.74.3-10.1ubuntu5+esm3"
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          {
            "binary_name": "libsoup-2.4-1",
            "binary_version": "2.74.3-10.1ubuntu5+esm3"
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            "binary_version": "2.74.3-10.1ubuntu5+esm3"
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            "binary_version": "2.74.3-10.1ubuntu5+esm3"
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        ]
      },
      "package": {
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        "name": "libsoup2.4",
        "purl": "pkg:deb/ubuntu/libsoup2.4@2.74.3-10.1ubuntu5+esm3?arch=source\u0026distro=esm-apps/resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
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          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.74.3-10.1ubuntu4",
        "2.74.3-10.1ubuntu5",
        "2.74.3-10.1ubuntu5+esm1",
        "2.74.3-10.1ubuntu5+esm2",
        "2.74.3-10.1ubuntu5+esm3"
      ]
    }
  ],
  "aliases": [],
  "details": "A flaw was found in SoupServer (libsoup). When an HTTP/1.x client sends a request with Expect: 100-continue and a request body, and SoupServer returns an early final (non-1xx) response before the body is read, the server neither drains the declared body bytes nor closes the connection. On a keep-alive connection, those leftover bytes are interpreted as a subsequent HTTP request. A remote, unauthenticated attacker can place a complete HTTP request in the body and cause SoupServer to process that smuggled request, leading to unintended request handling.",
  "id": "UBUNTU-CVE-2026-103399",
  "modified": "2026-10-08T09:54:47Z",
  "published": "2026-09-30T18:18:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-103399"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-103399"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2543949"
    },
    {
      "type": "REPORT",
      "url": "https://gitlab.gnome.org/GNOME/libsoup/-/work_items/539"
    },
    {
      "type": "REPORT",
      "url": "https://gitlab.gnome.org/GNOME/libsoup/-/merge_requests/560"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2026-103399"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-103399"
  ]
}

CVE-2026-103399 (GCVE-0-2026-103399)

Vulnerability from cvelistv5 – Published: 2026-09-30 17:42 – Updated: 2026-09-30 19:11

Title

Libsoup: soupserver: http/1 request smuggling via undrained expect: 100-continue body

Summary

Severity

5.3 (Medium)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-30 19:10 UTC

CWE

CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

Assigner

redhat redhat root Scorecard

References

2 references

URL	Tags
https://access.redhat.com/security/cve/CVE-2026-103399	vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2543949	issue-trackingx_refsource_REDHAT

Impacted products

5 products

Vendor	Product	Version
Red Hat	Red Hat Enterprise Linux 10	cpe:/o:redhat:enterprise_linux:10
Red Hat	Red Hat Enterprise Linux 6	cpe:/o:redhat:enterprise_linux:6
Red Hat	Red Hat Enterprise Linux 7	cpe:/o:redhat:enterprise_linux:7
Red Hat	Red Hat Enterprise Linux 8	cpe:/o:redhat:enterprise_linux:8
Red Hat	Red Hat Enterprise Linux 9	cpe:/o:redhat:enterprise_linux:9

Date Public

2026-09-29 00:00

Credits

Red Hat would like to thank Jianqiang (Stark) Li for reporting this issue.

Show details on NVD website

JSON

To clipboard

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        {
          "lang": "en",
          "value": "A flaw was found in SoupServer (libsoup). When an HTTP/1.x client sends a request with Expect: 100-continue and a request body, and SoupServer returns an early final (non-1xx) response before the body is read, the server neither drains the declared body bytes nor closes the connection. On a keep-alive connection, those leftover bytes are interpreted as a subsequent HTTP request. A remote, unauthenticated attacker can place a complete HTTP request in the body and cause SoupServer to process that smuggled request, leading to unintended request handling."
        }
      ],
      "metrics": [
        {
          "other": {
            "content": {
              "namespace": "https://access.redhat.com/security/updates/classification/",
              "value": "Moderate"
            },
            "type": "Red Hat severity rating"
          }
        },
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
            "version": "3.1"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-444",
              "description": "Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-30T17:42:31.307Z",
        "orgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
        "shortName": "redhat"
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          "tags": [
            "vdb-entry",
            "x_refsource_REDHAT"
          ],
          "url": "https://access.redhat.com/security/cve/CVE-2026-103399"
        },
        {
          "name": "RHBZ#2543949",
          "tags": [
            "issue-tracking",
            "x_refsource_REDHAT"
          ],
          "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2543949"
        }
      ],
      "timeline": [
        {
          "lang": "en",
          "time": "2026-09-29T00:00:00.000Z",
          "value": "Reported to Red Hat."
        },
        {
          "lang": "en",
          "time": "2026-09-29T00:00:00.000Z",
          "value": "Made public."
        }
      ],
      "title": "Libsoup: soupserver: http/1 request smuggling via undrained expect: 100-continue body",
      "workarounds": [
        {
          "lang": "en",
          "value": "To mitigate this do not expose SoupServer to untrusted networks; prefer terminating proxies or internal-only listeners. If SoupServer must sit behind a reverse proxy, disable backend connection reuse/pooling across clients so an undrained body cannot prepend to another client\u0027s request."
        }
      ],
      "x_generator": {
        "engine": "cvelib 1.8.0"
      },
      "x_redhatCweChain": "CWE-444: Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027)"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
    "assignerShortName": "redhat",
    "cveId": "CVE-2026-103399",
    "datePublished": "2026-09-30T17:42:31.307Z",
    "dateReserved": "2026-09-30T14:31:37.532Z",
    "dateUpdated": "2026-09-30T19:11:12.971Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Confirmed: The vulnerability has been validated from an analyst's perspective.
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Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
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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

UBUNTU-CVE-2026-103399 (CVE-2026-103399)

CVE-2026-103399 (GCVE-0-2026-103399)

Tags

Sightings

Nomenclature

Related by attack behaviour