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Fencer Intel
critical 9.2

CVE-2026-63382 json

libevent evhttp: Multiple HTTP Parser Bugs Enable Request Smuggling

published 4mo ago modified 16d ago also EUVD-2026-63505 , GHSA-q39v-w2g7-gr8j

Unreviewed: the maintainers' own advisory

Published by the maintainers on their GitHub repository libevent/libevent. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.

cvss
9.2
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
2.0%
EPSS 2.0% chance of exploitation in 30 days, percentile 80%
public exploits
0
none known

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 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.

Patch / fix

  • libevent_project libevent 2.1.13, 2.2.2-alpha
  • libevent Debian 12 2.1.12-stable-8+deb12u1
  • libevent Debian 13 2.1.13-stable-1~deb13u1
  • libevent Debian 14 2.1.13-stable-1

debian advisories DEBIAN-CVE-2026-63382

  • libevent Ubuntu 22.04 LTS 2.1.12-stable-1ubuntu0.1
  • libevent Ubuntu 24.04 LTS 2.1.12-stable-9ubuntu2.1
  • libevent Ubuntu 26.04 LTS 2.1.12-stable-10ubuntu0.1
  • libevent Ubuntu Pro 14.04 LTS 2.0.21-stable-1ubuntu1.14.04.2+esm1
  • libevent Ubuntu Pro 16.04 LTS 2.0.21-stable-2ubuntu0.16.04.1+esm1
  • libevent Ubuntu Pro 18.04 LTS 2.1.8-stable-4ubuntu0.1~esm1
  • libevent Ubuntu Pro 20.04 LTS 2.1.11-stable-1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2026-63382

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libevent RHEL 9 2.1.13-1.el9_8
  • libevent RHEL 8 2.1.8-11.el8_10
  • libevent RHEL 10.2 2.1.13-1.el10_2
  • libevent hummingbird 1 2.1.13-0.1.hum1

red hat advisories RHSA-2026:67910RHSA-2026:67908RHSA-2026:67909RHSA-2026:63388

  • libevent openSUSE Tumbleweed 2.1.13-1.1

opensuse advisories openSUSE-SU-2026:12330-1

  • libevent AlmaLinux 8 2.1.8-11.el8_10
  • libevent AlmaLinux 10 2.1.13-1.el10_2
  • libevent AlmaLinux 9 2.1.13-1.el9_8

almalinux advisories ALSA-2026:67908ALSA-2026:67909ALSA-2026:67910

  • libevent Rocky Linux 10 2.1.13-1.el10_2
  • libevent Rocky Linux 8 2.1.8-11.el8_10
  • libevent Rocky Linux 9 2.1.13-1.el9_8

rocky linux advisories RLSA-2026:67909RLSA-2026:67908RLSA-2026:67910

  • libevent Azure Linux 3.0 2.1.13-1
  • mysql Azure Linux 3.0 8.0.46-2
  • ntp Azure Linux 3.0 4.2.8p17-3

azure linux advisories AZL-96944AZL-97536AZL-97560

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Is CVE-2026-63382 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-63382 updated cvss 7.7

libevent: libevent: Multiple HTTP Parser Bugs Enable Request Smuggling

  • Red Hat Enterprise Linux 6 libevent, libevent2
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 libevent Red Hat OpenShift Container Platform 4 rhcos, openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 5 rhcos, openshift/ose-rhel-coreos-9
    affected: workaround, no fix available
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.20 cert-manager/cert-manager-operator-rhel9 1790272426, cert-manager/cert-manager-operator-rhel9 1790589855, cert-manager/jetstack-cert-manager-rhel9 1790223279, cert-manager/jetstack-cert-manager-rhel9 1790589912, cert-manager/cert-manager-istio-csr-rhel9 1790223719, cert-manager/cert-manager-istio-csr-rhel9 1790589914, +1 more
    fixed: vendor fix RHSA-2026:72475
  • Red Hat Enterprise Linux AppStream (v. 8) libevent-devel 2.1.8-11.el8_10, libevent-debuginfo 2.1.8-11.el8_10, libevent-debugsource 2.1.8-11.el8_10
    fixed: vendor fix RHSA-2026:67908
  • Red Hat Enterprise Linux AppStream (v. 9) libevent-doc 2.1.13-1.el9_8, libevent-devel 2.1.13-1.el9_8, libevent-debuginfo 2.1.13-1.el9_8, libevent-debugsource 2.1.13-1.el9_8
    fixed: vendor fix RHSA-2026:67910
  • Red Hat Enterprise Linux AppStream (v. 10) libevent-doc 2.1.13-1.el10_2, libevent-devel 2.1.13-1.el10_2, libevent-debuginfo 2.1.13-1.el10_2, libevent-debugsource 2.1.13-1.el10_2
    fixed: vendor fix RHSA-2026:67909
  • Red Hat Enterprise Linux BaseOS (v. 8) libevent 2.1.8-11.el8_10
    fixed: vendor fix RHSA-2026:67908
  • Red Hat Enterprise Linux BaseOS (v. 9) libevent 2.1.13-1.el9_8
    fixed: vendor fix RHSA-2026:67910
show 5 more
  • Red Hat Enterprise Linux BaseOS (v. 10) libevent 2.1.13-1.el10_2
    fixed: vendor fix RHSA-2026:67909
  • Red Hat Hardened Images libevent 2.1.13-0.1.hum1
    fixed: vendor fix RHSA-2026:63388
  • Red Hat OpenShift Container Platform 4.22 rhcos 4.22.9.8.202610241758
    fixed: vendor fix RHSA-2026:89197
  • Red Hat Update Infrastructure 5 rhui5/cds-rhel9 1790241954, rhui5/rhua-rhel9 1790242004, rhui5/haproxy-rhel9 1790241900, rhui5/installer-rhel9 1790241922, rhui5/cds-kubernetes-rhel9 1790241897
    fixed: vendor fix RHSA-2026:71603
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.20 cert-manager/jetstack-cert-manager-acmesolver-rhel9 1790223630 Red Hat OpenShift Service Mesh 3 istio-proxy-selinux, istio-proxy 1.30.5-1.el9 Red Hat OpenShift AI (RHOAI) rhoai/odh-llama-stack-k8s-operator-rhel9
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
total
Assessed
2mo ago

Exploit prediction

1.99% chance of exploitation in the next 30 days, higher than 80% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/libevent/libevent/security/advisories/GHSA-q39v-w2g7-gr8j referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 9.2 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
CNA 4.0 9.2 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • libevent libevent

Classification

Weakness
  • CWE-444 Inconsistent Interpretation of HTTP Requests

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of libevent/libevent published their own advisory on GitHub. Reviewed sources take precedence over it.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.