Vulnerability-Lookup

CVE-2026-63379 (GCVE-0-2026-63379)

Vulnerability from cvelistv5 – Published: 2026-08-20 17:55 – Updated: 2026-08-25 15:14

Title

Libevent: HTTP Header smuggling

Summary

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent processes chunked HTTP trailers in http.c through evhttp_read_trailer and merges them into request headers. The fix introduces evhttp_parse_headers_impl_ and a temporary trailer header list. An unauthenticated remote attacker can place security-sensitive fields in trailers so that an upstream proxy and the libevent application interpret different effective headers, enabling header smuggling, authorization bypass, proxy-header spoofing, or cache poisoning. The fix parses trailers into a temporary header list and discards them instead of merging them into req->input_headers. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

Severity

6.3 (Medium)


                        
                          CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-25 15:14 UTC

CWE

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

Assigner

GitHub_M mitre root

References

5 references

URL	Tags
https://github.com/libevent/libevent/security/adv…	x_refsource_CONFIRM
https://github.com/libevent/libevent/commit/87e8e…	x_refsource_MISC
https://github.com/libevent/libevent/commit/b8470…	x_refsource_MISC
https://github.com/libevent/libevent/releases/tag…	x_refsource_MISC
https://github.com/libevent/libevent/releases/tag…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
libevent	libevent	Affected: < 2.1.13 Affected: >= 2.2.0-alpha, < 2.2.2-alpha	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-63379

Vulnerability from fkie_nvd - Published: 2026-08-20 18:16 - Updated: 2026-09-09 21:19

Severity

6.3 (Medium) - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/libevent/libevent/commit/87e8e44fa774e9677b089b1a5114ee68aefa1636
	security-advisories@github.com	https://github.com/libevent/libevent/commit/b847071141b3827900d536594ec9045eb0a4c485
	security-advisories@github.com	https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable
	security-advisories@github.com	https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha
	security-advisories@github.com	https://github.com/libevent/libevent/security/advisories/GHSA-2gmv-p5m7-98p6

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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      "affectedData": [
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          "product": "libevent",
          "vendor": "libevent",
          "versions": [
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    }
  ],
  "id": "CVE-2026-63379",
  "lastModified": "2026-09-09T21:19:49.197",
  "metrics": {
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          "baseScore": 6.3,
          "baseSeverity": "MEDIUM",
          "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",
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    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/libevent/libevent/security/advisories/GHSA-2gmv-p5m7-98p6"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-444"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

MSRC_CVE-2026-63379

Vulnerability from csaf_microsoft - Published: 2026-08-22 01:03 - Updated: 2026-08-25 01:04

Summary

Libevent: HTTP Header smuggling

Scope

1 vulnerability in this advisory, including CVE-2026-63379.

CVE-2026-63379

Known affected: 5 products

Open the full advisory

RHSA-2026:60853

Vulnerability from csaf_redhat - Published: 2026-08-29 13:59 - Updated: 2026-09-11 16:55

Summary

Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update

Severity

Important

Scope

5 vulnerabilities in this advisory, including CVE-2026-63379.

CVE-2026-63379

A flaw was found in Libevent, an event notification library. An unauthenticated remote attacker can exploit a vulnerability where chunked HTTP (Hypertext Transfer Protocol) trailers are incorrectly merged into request headers. This allows the attacker to place security-sensitive fields in trailers, causing an upstream proxy and the Libevent application to interpret different effective headers. This can lead to header smuggling, authorization bypass, proxy-header spoofing, or cache poisoning.

6.5 (Medium)


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

Fixed: 4 products

https://access.redhat.com/errata/RHSA-2026:60853

Open the full advisory

ubuntu-cve-2026-63379

Vulnerability from osv_ubuntu

Published

2026-08-20 18:16

Modified

2026-09-02 16:20

Summary

Details

Severity

6.3 (Medium)


                    
                      CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-63379	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-63379	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libevent-2.0-5",
            "binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm1"
          },
          {
            "binary_name": "libevent-core-2.0-5",
            "binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm1"
          },
          {
            "binary_name": "libevent-extra-2.0-5",
            "binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm1"
          },
          {
            "binary_name": "libevent-openssl-2.0-5",
            "binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm1"
          },
          {
            "binary_name": "libevent-pthreads-2.0-5",
            "binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:14.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.0.21-stable-1ubuntu1.14.04.2+esm1?arch=source\u0026distro=esm-infra-legacy/trusty"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.0.21-stable-1",
        "2.0.21-stable-1ubuntu1",
        "2.0.21-stable-1ubuntu1.14.04.1",
        "2.0.21-stable-1ubuntu1.14.04.2",
        "2.0.21-stable-1ubuntu1.14.04.2+esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libevent-2.0-5",
            "binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm1"
          },
          {
            "binary_name": "libevent-core-2.0-5",
            "binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm1"
          },
          {
            "binary_name": "libevent-extra-2.0-5",
            "binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm1"
          },
          {
            "binary_name": "libevent-openssl-2.0-5",
            "binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm1"
          },
          {
            "binary_name": "libevent-pthreads-2.0-5",
            "binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:16.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.0.21-stable-2ubuntu0.16.04.1+esm1?arch=source\u0026distro=esm-infra-legacy/xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.0.21-stable-2",
        "2.0.21-stable-2ubuntu0.16.04.1",
        "2.0.21-stable-2ubuntu0.16.04.1+esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libevent-2.1-6",
            "binary_version": "2.1.8-stable-4ubuntu0.1~esm1"
          },
          {
            "binary_name": "libevent-core-2.1-6",
            "binary_version": "2.1.8-stable-4ubuntu0.1~esm1"
          },
          {
            "binary_name": "libevent-extra-2.1-6",
            "binary_version": "2.1.8-stable-4ubuntu0.1~esm1"
          },
          {
            "binary_name": "libevent-openssl-2.1-6",
            "binary_version": "2.1.8-stable-4ubuntu0.1~esm1"
          },
          {
            "binary_name": "libevent-pthreads-2.1-6",
            "binary_version": "2.1.8-stable-4ubuntu0.1~esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:18.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.1.8-stable-4ubuntu0.1~esm1?arch=source\u0026distro=esm-infra/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.1.8-stable-4",
        "2.1.8-stable-4build1",
        "2.1.8-stable-4ubuntu0.1~esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libevent-2.1-7",
            "binary_version": "2.1.11-stable-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libevent-core-2.1-7",
            "binary_version": "2.1.11-stable-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libevent-extra-2.1-7",
            "binary_version": "2.1.11-stable-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libevent-openssl-2.1-7",
            "binary_version": "2.1.11-stable-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libevent-pthreads-2.1-7",
            "binary_version": "2.1.11-stable-1ubuntu0.1~esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:20.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.1.11-stable-1ubuntu0.1~esm1?arch=source\u0026distro=esm-infra/focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.1.8-stable-4build1",
        "2.1.11-stable-1~exp0",
        "2.1.11-stable-1",
        "2.1.11-stable-1ubuntu0.1~esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libevent-2.1-7",
            "binary_version": "2.1.12-stable-1ubuntu0.1"
          },
          {
            "binary_name": "libevent-core-2.1-7",
            "binary_version": "2.1.12-stable-1ubuntu0.1"
          },
          {
            "binary_name": "libevent-extra-2.1-7",
            "binary_version": "2.1.12-stable-1ubuntu0.1"
          },
          {
            "binary_name": "libevent-openssl-2.1-7",
            "binary_version": "2.1.12-stable-1ubuntu0.1"
          },
          {
            "binary_name": "libevent-pthreads-2.1-7",
            "binary_version": "2.1.12-stable-1ubuntu0.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.1.12-stable-1ubuntu0.1?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.1.12-stable-1",
        "2.1.12-stable-1build1",
        "2.1.12-stable-1build2",
        "2.1.12-stable-1build3",
        "2.1.12-stable-1ubuntu0.1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libevent-2.1-7t64",
            "binary_version": "2.1.12-stable-9ubuntu2.1"
          },
          {
            "binary_name": "libevent-core-2.1-7t64",
            "binary_version": "2.1.12-stable-9ubuntu2.1"
          },
          {
            "binary_name": "libevent-extra-2.1-7t64",
            "binary_version": "2.1.12-stable-9ubuntu2.1"
          },
          {
            "binary_name": "libevent-openssl-2.1-7t64",
            "binary_version": "2.1.12-stable-9ubuntu2.1"
          },
          {
            "binary_name": "libevent-pthreads-2.1-7t64",
            "binary_version": "2.1.12-stable-9ubuntu2.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.1.12-stable-9ubuntu2.1?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.1.12-stable-9",
        "2.1.12-stable-9ubuntu2",
        "2.1.12-stable-9ubuntu2.1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libevent-2.1-7t64",
            "binary_version": "2.1.12-stable-10ubuntu0.1"
          },
          {
            "binary_name": "libevent-core-2.1-7t64",
            "binary_version": "2.1.12-stable-10ubuntu0.1"
          },
          {
            "binary_name": "libevent-extra-2.1-7t64",
            "binary_version": "2.1.12-stable-10ubuntu0.1"
          },
          {
            "binary_name": "libevent-openssl-2.1-7t64",
            "binary_version": "2.1.12-stable-10ubuntu0.1"
          },
          {
            "binary_name": "libevent-pthreads-2.1-7t64",
            "binary_version": "2.1.12-stable-10ubuntu0.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.1.12-stable-10ubuntu0.1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.1.12-stable-10build1",
        "2.1.12-stable-10build2",
        "2.1.12-stable-10ubuntu0.1"
      ]
    }
  ],
  "aliases": [],
  "details": "Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent processes chunked HTTP trailers in http.c through evhttp_read_trailer and merges them into request headers. The fix introduces evhttp_parse_headers_impl_ and a temporary trailer header list. An unauthenticated remote attacker can place security-sensitive fields in trailers so that an upstream proxy and the libevent application interpret different effective headers, enabling header smuggling, authorization bypass, proxy-header spoofing, or cache poisoning. The fix parses trailers into a temporary header list and discards them instead of merging them into req-\u003einput_headers. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.",
  "id": "UBUNTU-CVE-2026-63379",
  "modified": "2026-09-02T16:20:06Z",
  "published": "2026-08-20T18:16:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-63379"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-63379"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-63379"
  ]
}

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.

Detection rules are retrieved from Rulezet.

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-2026-63379 (GCVE-0-2026-63379)

FKIE_CVE-2026-63379

MSRC_CVE-2026-63379

RHSA-2026:60853

ubuntu-cve-2026-63379

Vulnerability from osv_ubuntu

Tags

Sightings

Nomenclature

Related by attack behaviour