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.
CVE-2026-63379
MEDIUMPre-NVD 6.36.3—Trending — 3 sources updated this week
EchelonGraph scoreMEDIUM confidence
This medium-severity CVE scores 6.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5%, top 58% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: epss, secondary
6.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
- Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 6.3Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 6.3
- EG Score
- 6.3(medium)
- EG Risk
- 44(Track)EG Risk 44/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity63% × 45%Exploitation1% × 40%Automatability100% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 1%
- EPSS %ILE
- 42%
- KEV
- Not listed
Published
August 20, 2026
Last Modified
August 25, 2026
Advisory Details (5)
Auto-updated Aug 20, 2026Patch available. Sources: github, github_commit, github_release.
github_release Patch Available
Libevent 2.2.2-alpha
Patch available: libevent/libevent release-2.2.2-alpha
https://github.com/libevent/libevent/releases/tag/release-2.2.2-alphagithub_release Patch Available
Libevent 2.1.13-stable
Patch available: libevent/libevent release-2.1.13-stable
https://github.com/libevent/libevent/releases/tag/release-2.1.13-stablegithub_commit Patch Available
commit b847071141b3 (libevent/libevent)
Patch available: libevent/libevent release-2.2.2-alpha (contains commit b847071141b3)
https://github.com/libevent/libevent/commit/b847071141b3827900d536594ec9045eb0a4c485github_commit Patch Available
commit 87e8e44fa774 (libevent/libevent)
Patch available: libevent/libevent release-2.1.13-stable (contains commit 87e8e44fa774)
https://github.com/libevent/libevent/commit/87e8e44fa774e9677b089b1a5114ee68aefa1636github Patch Available
HTTP Header smuggling · Advisory · libevent/libevent · GitHub
https://github.com/libevent/libevent/security/advisories/GHSA-2gmv-p5m7-98p6Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 11× in last 7d / 11× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-08-25 16:26 UTCEG score recompute
- 2026-08-25 15:31 UTCEG score recompute
- 2026-08-25 13:49 UTCEPSS rescore
- 2026-08-24 21:31 UTCEG score recompute
- 2026-08-23 20:43 UTCEG score recompute
- 2026-08-23 00:19 UTCEPSS rescore
- 2026-08-22 19:55 UTCEG score recompute
- 2026-08-21 23:49 UTCEPSS rescore
- 2026-08-20 18:17 UTCEG score recompute
- 2026-08-20 18:07 UTCEG score recompute
- 2026-08-20 18:06 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Same CWE
10 shownCWE-444
Frequently asked(5)
What is CVE-2026-63379?
CVE-2026-63379 is a medium vulnerability published on August 20, 2026. 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 evhttpreadtrailer and merges them into request headers. The fix introduces evhttpparseheadersimpl and a temporary trailer header list. An unauthenticated remote…
When was CVE-2026-63379 disclosed?
CVE-2026-63379 was first published in the National Vulnerability Database on August 20, 2026, with the most recent update on August 25, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-63379 actively exploited?
CVE-2026-63379 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 58.3% of all scored CVEs.
What is the CVSS score of CVE-2026-63379?
CVE-2026-63379 has a CVSS v3 base score of 6.3 (NVD).
How do I remediate CVE-2026-63379?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-63379, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-63379
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