Description
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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| libevent | libevent | < 2.1.13, >= 2.2.0-alpha, < 2.2.2-alpha | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | libevent | 2.1.13-stable-1 | — |
| Debian 13 | libevent | 2.1.13-stable-1~deb13u1 | — |
| Debian 12 | libevent | 2.1.12-stable-8+deb12u1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | libevent | No fix yet | — |
| Ubuntu 26.04 LTS | libevent | No fix yet | — |
| Ubuntu 24.04 LTS | libevent | No fix yet | — |
| Ubuntu 22.04 LTS | libevent | No fix yet | — |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | libevent | No fix yet | — |
| Ubuntu Pro 18.04 LTS | libevent | No fix yet | — |
| Ubuntu Pro 16.04 LTS | libevent | No fix yet | — |
| Ubuntu Pro 14.04 LTS | libevent | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 10 | libevent +2 | 2.1.13-1.el10_2 | RHSA-2026:67909 |
| RHEL 9 | libevent +2 | 2.1.13-1.el9_8 | RHSA-2026:67910 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat Hardened Images 1 | libevent +2 | 2.1.12-19.1.hum1 | RHSA-2026:60853 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 10 | libevent +2 | 2.1.13-1.el10_2 | ALSA-2026:67909 |
| AlmaLinux 9 | libevent +2 | 2.1.13-1.el9_8 | ALSA-2026:67910 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 10 | libevent | 2.1.13-1.el10_2 | RLSA-2026:67909 |
| Rocky Linux 9 | libevent | 2.1.13-1.el9_8 | RLSA-2026:67910 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | libevent | 2.1.13-1.1 | openSUSE-SU-2026:12330-1 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | libevent | 2.1.13-1 | — |
| Azure Linux 3 | libtevent | No fix yet | — |
| Azure Linux 3 | mysql | 8.0.46-2 | — |
| Azure Linux 3 | ntp | 4.2.8p17-3 | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 10 | libevent +2 | 2.1.13-1.el10_2 | ELSA-2026-67909 |
| Oracle Linux 9 | libevent +2 | 2.1.13-1.el9_8 | ELSA-2026-67910 |
Advisories 11
- WID-SEC-2026-3419 Red Hat Enterprise Linux (corosync, libevent, libsoup): Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 12, 2026
- openSUSE-SU-2026:12330-1 libevent-2_1-7-2.1.13-1.1 on GA media SUSE / openSUSE Security Updates · Oct 29, 2026
- ALSA-2026:67910 Important: libevent security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2026:67909 Important: libevent security update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2026:67910 Red Hat Security Advisory: libevent security update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:67909 Red Hat Security Advisory: libevent security update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:60853 Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update Red Hat Security Advisories (RHSA) · Oct 6, 2026
- RLSA-2026:67909 Important: libevent security update Rocky Linux Security Advisories · Sep 17, 2026
- RLSA-2026:67910 Important: libevent security update Rocky Linux Security Advisories · Sep 17, 2026
- ELSA-2026-67909 Important: libevent security update (Oracle Linux 10) Oracle Linux Security Advisories (ELSA) · Sep 16, 2026
- ELSA-2026-67910 Important: libevent security update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Sep 16, 2026
References
- https://github.com/libevent/libevent/security/advisories/GHSA-2gmv-p5m7-98p6
- https://github.com/libevent/libevent/commit/87e8e44fa774e9677b089b1a5114ee68aefa1636
- https://github.com/libevent/libevent/commit/b847071141b3827900d536594ec9045eb0a4c485
- https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable
- https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha