libevent evhttp: Multiple HTTP Parser Bugs Enable Request Smuggling
Summary
| CVE | CVE-2026-63382 |
|---|---|
| State | PUBLISHED |
| Assigner | GitHub_M |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-08-20 18:16:35 UTC |
| Updated | 2026-08-20 20:17:45 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 9.2 CRITICAL from [email protected]
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
Problem Types: CWE-444 | CWE-444 CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | [email protected] | Secondary | 9.2 | CRITICAL | 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/C... |
| 4.0 | CNA | DECLARED | 9.2 | CRITICAL | 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 |
CVSS v4.0 Breakdown
Attack Vector
NetworkAttack Complexity
LowAttack Requirements
PresentPrivileges Required
NoneUser Interaction
NoneConfidentiality
HighIntegrity
HighAvailability
LowSub Conf.
LowSub Integrity
LowSub Availability
NoneCVSS: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
Vendor Declared Affected Products
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/libevent/libevent/releases/tag/release-2.1.13-stable | [email protected] | github.com | |
| github.com/libevent/libevent/commit/5119ceb00557bf007f9065709e852686f3c0... | [email protected] | github.com | |
| github.com/libevent/libevent/security/advisories/GHSA-q39v-w2g7-gr8j | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | github.com | |
| github.com/libevent/libevent/releases/tag/release-2.2.2-alpha | [email protected] | github.com | |
| github.com/libevent/libevent/commit/ac38703b2d312200c4f967f02936af0118d3... | [email protected] | github.com | |
| github.com/libevent/libevent/commit/10abb34b8dc3e1184de315dd261ce4b77563... | [email protected] | github.com | |
| github.com/libevent/libevent/commit/83ba67373032334559b82409db035dd8c3cc... | [email protected] | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.