CVE-2026-63379

MEDIUMPre-NVD 6.36.3
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This medium-severity CVE scores 6.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.7% (53rd percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Trending — 3 sources updated this week

Also known asEUVD-2026-63562 (ENISA EUVD)Source: ENISA EUVD

6.3EG
EchelonGraph verdictMonitorRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.7%CVSS: 6.3Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
6.3
EG Score
6.3MEDIUMmedium confidence
EG Risk
44
EG Risk 44/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity63% × 45%
Impact severity (EG Severity): CVSS 6.3 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.7% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.7%
EPSS %ILE
53rd
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (6.3): severity, escalated by confirmed exploitation. This CVE's 6.3 is its impact severity (EG Severity), not escalated.

EG Severity
6.3 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source · CVSS v3.0 or v3.1
EG Likelihood
0.7% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-29). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

August 20, 2026

Last Modified

October 26, 2026

Advisory Details (5)

Auto-updated Aug 20, 2026
Patch 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-alpha
GitHub 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-stable
GitHub 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/b847071141b3827900d536594ec9045eb0a4c485
GitHub 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/87e8e44fa774e9677b089b1a5114ee68aefa1636
GitHub advisoryMentions a patch (unverified)

HTTP Header smuggling · Advisory · libevent/libevent · GitHub

https://github.com/libevent/libevent/security/advisories/GHSA-2gmv-p5m7-98p6

Patch Availability(10)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatcert-manager/cert-manager-operator-rhel9:17905898552026-09-28redhat
redhatcert-manager/jetstack-cert-manager-rhel9:17905899122026-09-28redhat
redhatcert-manager/cert-manager-istio-csr-rhel9:17905899142026-09-28redhat
redhatcert-manager/cert-manager-operator-rhel9:17902724262026-09-28redhat
redhatcert-manager/cert-manager-istio-csr-rhel9:17902237192026-09-28redhat
redhatcert-manager/jetstack-cert-manager-rhel9:17902232792026-09-28redhat
redhatrhui5/rhua-rhel9:17902420042026-09-24redhat
redhatlibevent-0:2.1.13-1.el10_22026-09-16redhat
redhatlibevent-0:2.1.13-1.el9_82026-09-16redhat
redhatlibevent-main-2.1.12-19.1.hum12026-08-29redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
libevent2.1.12-stable-8
  • every version up to 2.1.12-stable-8+deb12u1: fixed in 2.1.12-stable-8+deb12u1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
libevent2.1.12-stable-10
  • every version up to 2.1.13-stable-1~deb13u1: fixed in 2.1.13-stable-1~deb13u1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
libevent2.1.12-stable-10, 2.1.13-stable-1~deb13u1
  • every version up to 2.1.13-stable-1: fixed in 2.1.13-stable-1
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 9× in last 7d / 54× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 97 of 151 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 3 repeat rows among the latest 100 are merged into the row they repeat. The 54 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  2. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  3. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  4. 2026-10-29 16:41 UTCEG score recompute
  5. 2026-10-29 16:41 UTCVendor advisory
  6. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  7. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  8. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  9. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  10. 2026-10-26 10:27 UTCEG score recompute
  11. 2026-10-26 10:27 UTCVendor advisory
  12. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  13. 2026-10-25 14:13 UTCEG score recompute
  14. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  15. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  16. 2026-10-22 19:49 UTCEG score recompute
  17. 2026-10-22 19:49 UTCVendor advisory
  18. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  19. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  20. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  21. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  22. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  23. 2026-10-18 03:23 UTCEG score recompute
  24. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  25. 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
Show 72 more
  1. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  2. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  3. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  4. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  5. 2026-10-12 15:49 UTCEG score recompute
  6. 2026-10-11 19:33 UTCEG score recompute
  7. 2026-10-11 16:48 UTCEG score recompute
  8. 2026-10-11 14:10 UTCEG score recompute
  9. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  10. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  11. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  12. 2026-10-09 08:27 UTCEG score recompute
  13. 2026-10-09 08:27 UTCVendor advisory
  14. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  15. 2026-10-08 05:19 UTCEG score recompute
  16. 2026-10-08 05:19 UTCVendor advisory
  17. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  18. 2026-10-07 04:13 UTCEG score recompute
  19. 2026-10-07 04:13 UTCVendor advisory
  20. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  21. 2026-10-06 03:24 UTCVendor advisory
  22. 2026-10-06 03:24 UTCEG score recompute
  23. 2026-10-06 03:24 UTCVendor advisory
  24. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  25. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  26. 2026-10-04 20:52 UTCVendor advisory
  27. 2026-10-03 16:47 UTCEG score recompute
  28. 2026-10-03 16:47 UTCVendor advisory
  29. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  30. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  31. 2026-10-02 09:50 UTCEG score recompute
  32. 2026-10-02 09:50 UTCVendor advisory
  33. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  34. 2026-10-01 09:01 UTCEG score recompute
  35. 2026-10-01 09:01 UTCVendor advisory
  36. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  37. 2026-09-30 08:13 UTCEG score recompute
  38. 2026-09-30 08:13 UTCVendor advisory
  39. 2026-09-29 04:39 UTCEG score recompute
  40. 2026-09-29 04:39 UTCVendor advisory
  41. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  42. 2026-09-28 03:50 UTCEG score recompute
  43. 2026-09-28 03:50 UTCVendor advisory
  44. 2026-09-27 03:00 UTCEG score recompute
  45. 2026-09-27 03:00 UTCVendor advisory
  46. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  47. 2026-09-25 13:09 UTCEG score recompute
  48. 2026-09-25 13:09 UTCVendor advisory
  49. 2026-09-24 12:21 UTCEG score recompute
  50. 2026-09-24 12:21 UTCVendor advisory
  51. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  52. 2026-09-23 11:31 UTCEG score recompute
  53. 2026-09-23 11:31 UTCVendor advisory
  54. 2026-09-22 10:43 UTCEG score recompute
  55. 2026-09-22 10:43 UTCVendor advisory
  56. 2026-09-21 09:49 UTCVendor advisory
  57. 2026-09-20 09:00 UTCEG score recompute
  58. 2026-09-20 09:00 UTCVendor advisory
  59. 2026-09-19 07:06 UTCEG score recompute
  60. 2026-09-19 07:06 UTCVendor advisory
  61. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  62. 2026-09-18 06:17 UTCEG score recompute
  63. 2026-09-18 06:17 UTCVendor advisory
  64. 2026-09-17 05:29 UTCEG score recompute
  65. 2026-09-17 05:29 UTCVendor advisory
  66. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  67. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  68. 2026-09-16 04:40 UTCVendor advisory
  69. 2026-09-15 03:35 UTCEG score recompute
  70. 2026-09-15 03:35 UTCVendor advisory
  71. 2026-09-14 02:45 UTCEG score recompute
  72. 2026-09-14 02:45 UTCVendor advisory

Frequently asked(5)

What is CVE-2026-63379?
CVE-2026-63379 is a medium-severity vulnerability; its CVE record was 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 evhttp_read_trailer and merges them into request headers. The fix introduces evhttp_parse_headers_impl_ and a temporary trailer header list. An unauthenticated…
When was the CVE record for CVE-2026-63379 published?
The CVE record for CVE-2026-63379 was published on August 20, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 26, 2026; the record at its source may have been updated since.
Is CVE-2026-63379 actively exploited?
CVE-2026-63379 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.7% probability of exploitation in the next 30 days (53rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-63379?
CVE-2026-63379 has a CVSS base score of 6.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-63379?
A fix for CVE-2026-63379 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-63379 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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