UBUNTU-CVE-2026-63379 (CVE-2026-63379)
Vulnerability from osv_ubuntu – Published: 2026-08-20 18:16 – Updated: 2026-09-29 01:40 – Source website
VLAI
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->input_headers. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.
Severity
N/A (UNKNOWN)
References
| URL | Type | |
|---|---|---|
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libevent-2.0-5",
"binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm2"
},
{
"binary_name": "libevent-core-2.0-5",
"binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm2"
},
{
"binary_name": "libevent-extra-2.0-5",
"binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm2"
},
{
"binary_name": "libevent-openssl-2.0-5",
"binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm2"
},
{
"binary_name": "libevent-pthreads-2.0-5",
"binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm2"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:14.04:LTS",
"name": "libevent",
"purl": "pkg:deb/ubuntu/libevent@2.0.21-stable-1ubuntu1.14.04.2+esm2?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",
"2.0.21-stable-1ubuntu1.14.04.2+esm2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libevent-2.0-5",
"binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm2"
},
{
"binary_name": "libevent-core-2.0-5",
"binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm2"
},
{
"binary_name": "libevent-extra-2.0-5",
"binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm2"
},
{
"binary_name": "libevent-openssl-2.0-5",
"binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm2"
},
{
"binary_name": "libevent-pthreads-2.0-5",
"binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm2"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:16.04:LTS",
"name": "libevent",
"purl": "pkg:deb/ubuntu/libevent@2.0.21-stable-2ubuntu0.16.04.1+esm2?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",
"2.0.21-stable-2ubuntu0.16.04.1+esm2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libevent-2.1-6",
"binary_version": "2.1.8-stable-4ubuntu0.1~esm2"
},
{
"binary_name": "libevent-core-2.1-6",
"binary_version": "2.1.8-stable-4ubuntu0.1~esm2"
},
{
"binary_name": "libevent-extra-2.1-6",
"binary_version": "2.1.8-stable-4ubuntu0.1~esm2"
},
{
"binary_name": "libevent-openssl-2.1-6",
"binary_version": "2.1.8-stable-4ubuntu0.1~esm2"
},
{
"binary_name": "libevent-pthreads-2.1-6",
"binary_version": "2.1.8-stable-4ubuntu0.1~esm2"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:18.04:LTS",
"name": "libevent",
"purl": "pkg:deb/ubuntu/libevent@2.1.8-stable-4ubuntu0.1~esm2?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",
"2.1.8-stable-4ubuntu0.1~esm2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libevent-2.1-7",
"binary_version": "2.1.11-stable-1ubuntu0.1~esm2"
},
{
"binary_name": "libevent-core-2.1-7",
"binary_version": "2.1.11-stable-1ubuntu0.1~esm2"
},
{
"binary_name": "libevent-extra-2.1-7",
"binary_version": "2.1.11-stable-1ubuntu0.1~esm2"
},
{
"binary_name": "libevent-openssl-2.1-7",
"binary_version": "2.1.11-stable-1ubuntu0.1~esm2"
},
{
"binary_name": "libevent-pthreads-2.1-7",
"binary_version": "2.1.11-stable-1ubuntu0.1~esm2"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:20.04:LTS",
"name": "libevent",
"purl": "pkg:deb/ubuntu/libevent@2.1.11-stable-1ubuntu0.1~esm2?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",
"2.1.11-stable-1ubuntu0.1~esm2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libevent-2.1-7",
"binary_version": "2.1.12-stable-1ubuntu0.2"
},
{
"binary_name": "libevent-core-2.1-7",
"binary_version": "2.1.12-stable-1ubuntu0.2"
},
{
"binary_name": "libevent-extra-2.1-7",
"binary_version": "2.1.12-stable-1ubuntu0.2"
},
{
"binary_name": "libevent-openssl-2.1-7",
"binary_version": "2.1.12-stable-1ubuntu0.2"
},
{
"binary_name": "libevent-pthreads-2.1-7",
"binary_version": "2.1.12-stable-1ubuntu0.2"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "libevent",
"purl": "pkg:deb/ubuntu/libevent@2.1.12-stable-1ubuntu0.2?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",
"2.1.12-stable-1ubuntu0.2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libevent-2.1-7t64",
"binary_version": "2.1.12-stable-9ubuntu2.2"
},
{
"binary_name": "libevent-core-2.1-7t64",
"binary_version": "2.1.12-stable-9ubuntu2.2"
},
{
"binary_name": "libevent-extra-2.1-7t64",
"binary_version": "2.1.12-stable-9ubuntu2.2"
},
{
"binary_name": "libevent-openssl-2.1-7t64",
"binary_version": "2.1.12-stable-9ubuntu2.2"
},
{
"binary_name": "libevent-pthreads-2.1-7t64",
"binary_version": "2.1.12-stable-9ubuntu2.2"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "libevent",
"purl": "pkg:deb/ubuntu/libevent@2.1.12-stable-9ubuntu2.2?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",
"2.1.12-stable-9ubuntu2.2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libevent-2.1-7t64",
"binary_version": "2.1.12-stable-10ubuntu0.2"
},
{
"binary_name": "libevent-core-2.1-7t64",
"binary_version": "2.1.12-stable-10ubuntu0.2"
},
{
"binary_name": "libevent-extra-2.1-7t64",
"binary_version": "2.1.12-stable-10ubuntu0.2"
},
{
"binary_name": "libevent-openssl-2.1-7t64",
"binary_version": "2.1.12-stable-10ubuntu0.2"
},
{
"binary_name": "libevent-pthreads-2.1-7t64",
"binary_version": "2.1.12-stable-10ubuntu0.2"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "libevent",
"purl": "pkg:deb/ubuntu/libevent@2.1.12-stable-10ubuntu0.2?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",
"2.1.12-stable-10ubuntu0.2"
]
}
],
"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": "2026-09-29T01:40:59Z",
"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"
]
}
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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.
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- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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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.
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.
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Related by attack behaviour
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