Description
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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| libevent | libevent | >= 2.2.0-alpha, < 2.2.2-alpha, < 2.1.13 | — |
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 26.04 LTS | libevent | 2.1.12-stable-10ubuntu0.1 | USN-8710-1 |
| Ubuntu 24.04 LTS | libevent | 2.1.12-stable-9ubuntu2.1 | USN-8710-1 |
| Ubuntu 22.04 LTS | libevent | 2.1.12-stable-1ubuntu0.1 | USN-8710-1 |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | libevent | 2.1.11-stable-1ubuntu0.1~esm1 | USN-8710-1 |
| Ubuntu Pro 18.04 LTS | libevent | 2.1.8-stable-4ubuntu0.1~esm1 | USN-8710-1 |
| Ubuntu Pro 16.04 LTS | libevent | 2.0.21-stable-2ubuntu0.16.04.1+esm1 | USN-8710-1 |
| Ubuntu Pro 14.04 LTS | libevent | 2.0.21-stable-1ubuntu1.14.04.2+esm1 | USN-8710-1 |
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 |
| RHEL 8 | libevent +2 | 2.1.8-11.el8_10 | RHSA-2026:67908 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat Hardened Images 1 | libevent +2 | 2.1.13-0.1.hum1 | RHSA-2026:63388 |
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 |
| AlmaLinux 8 | libevent +2 | 2.1.8-11.el8_10 | ALSA-2026:67908 |
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 |
| Rocky Linux 8 | libevent | 2.1.8-11.el8_10 | RLSA-2026:67908 |
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 |
| Oracle Linux 8 | libevent +2 | 2.1.8-11.el8_10 | ELSA-2026-67908 |
Advisories 16
- 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
- ALSA-2026:67908 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-2026:67908 Red Hat Security Advisory: libevent security update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:63388 Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RLSA-2026:67908 Important: libevent security update Rocky Linux Security Advisories · Sep 17, 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-2026-67908 Important: libevent security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · 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
- USN-8710-1 libevent vulnerabilities Ubuntu Security Notices (USN) · Sep 2, 2026
References
- https://github.com/libevent/libevent/security/advisories/GHSA-q39v-w2g7-gr8j
- https://github.com/libevent/libevent/commit/10abb34b8dc3e1184de315dd261ce4b77563cda6
- https://github.com/libevent/libevent/commit/5119ceb00557bf007f9065709e852686f3c0bb6e
- https://github.com/libevent/libevent/commit/83ba67373032334559b82409db035dd8c3cc1660
- https://github.com/libevent/libevent/commit/ac38703b2d312200c4f967f02936af0118d384a0
- https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable
- https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha