---
id: CVE-2026-63382
title: Libevent is an event notification library
summary: >-
  Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha,
  the libevent evhttp parser in http.c inconsistently handles duplicate
  Transfer-Encoding headers, comma-separated Transfer-Encoding values, and bare
  line feeds in…
severity: critical
cvss: 9.2
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:L/SI:L/SA:N'
cwe:
  - CWE-444
vendor: libevent
product: libevent
affected:
  - 'libevent >= 2.2.0-alpha, < 2.2.2-alpha'
  - libevent < 2.1.13
published: '2026-08-20'
updated: '2026-09-09'
sourceUpdated: '2026-09-09T21:19:49.197'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63382'
references:
  - url: >-
      https://github.com/libevent/libevent/commit/10abb34b8dc3e1184de315dd261ce4b77563cda6
    label: security-advisories@github.com
  - url: >-
      https://github.com/libevent/libevent/commit/5119ceb00557bf007f9065709e852686f3c0bb6e
    label: security-advisories@github.com
  - url: >-
      https://github.com/libevent/libevent/commit/83ba67373032334559b82409db035dd8c3cc1660
    label: security-advisories@github.com
  - url: >-
      https://github.com/libevent/libevent/commit/ac38703b2d312200c4f967f02936af0118d384a0
    label: security-advisories@github.com
  - url: 'https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable'
    label: security-advisories@github.com
  - url: 'https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha'
    label: security-advisories@github.com
  - url: >-
      https://github.com/libevent/libevent/security/advisories/GHSA-q39v-w2g7-gr8j
    label: security-advisories@github.com
  - url: >-
      https://github.com/libevent/libevent/security/advisories/GHSA-q39v-w2g7-gr8j
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63382.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-63382'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2520660'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-63382'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63382'
  - url: 'https://access.redhat.com/errata/RHSA-2026:67909'
  - url: 'https://access.redhat.com/errata/RHSA-2026:67908'
  - url: 'https://access.redhat.com/errata/RHSA-2026:67910'
  - url: 'https://access.redhat.com/errata/RHSA-2026:63388'
  - url: 'https://access.redhat.com/errata/RHSA-2026:71603'
tags:
  - nvd
  - cve.org
  - exploit-available
  - csaf
  - vex
  - red-hat
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-08-20T19:33:43.608585Z'
cvssSource: cna
ingestedAt: '2026-09-14T14:04:14.885Z'
epss: 0.00784
epssPercentile: 0.5417
patched:
  - enterprise_linux_appstream_v_10
  - enterprise_linux_appstream_v_8
  - enterprise_linux_appstream_v_9
  - enterprise_linux_baseos_v_10
  - enterprise_linux_baseos_v_8
  - enterprise_linux_baseos_v_9
  - hardened_images
scores:
  cna: 9.2
  vendor: 7.7
---

## Overview

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, the libevent evhttp parser in http.c inconsistently handles duplicate Transfer-Encoding headers, comma-separated Transfer-Encoding values, and bare line feeds in chunked framing. evhttp_find_header can select only the first header, evhttp_check_transfer_encoding_ was absent so the previous whole-string comparison fails to recognize valid lists ending in chunked, and evhttp_handle_chunked_read uses EVBUFFER_EOL_CRLF rather than EVBUFFER_EOL_CRLF_STRICT, accepting bare LF chunk terminators. When libevent is deployed behind a proxy that frames the same request differently, an unauthenticated remote attacker can desynchronize request boundaries and smuggle a second request, potentially bypassing access controls or poisoning caches. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **RHSA-2026:67909** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10) · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:67909)
- **RHSA-2026:67908** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 8), Red Hat Enterprise Linux BaseOS (v. 8) · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:67908)
- **RHSA-2026:67910** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9) · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:67910)
- **RHSA-2026:63388** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-03 · [advisory](https://access.redhat.com/errata/RHSA-2026:63388)
- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat OpenShift Container Platform 4 · updated 2026-09-24 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63382.json)
- **RHSA-2026:71603** · Red Hat · fixed in: Red Hat Update Infrastructure 5 · released 2026-09-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:71603)