CVE-2026-63381

MEDIUMPre-NVD 5.85.8—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2% (4th percentile of EPSS-scored CVEs). 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
Trending — 3 sources updated this week
5.8EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 5.8Exploit: 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 has a use-after-free in buffer.c when evbuffer_add_buffer_reference processes an output buffer whose out_total_len is zero. evbuffer_free_all_chains frees the initial empty chain without resetting outbuf->first, outbuf->last, or outbuf->last_with_datap, and APPEND_CHAIN_MULTICAST subsequently dereferences the dangling chain pointer. A caller that can drive this buffer state can cause memory corruption or a process crash. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

CVSS v3
5.8
EG Score
5.8MEDIUMmedium confidence
EG Risk
26
EG Risk 26/100

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 computed (value × EchelonGraph’s weight)
Severity58% × 45%
The EG Score, 5.8 of 10.
Exploitation0% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (CISA Vulnrichment) · Automatable no (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.
EPSS PROB
0.2%
EPSS %ILE
4th
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (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)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (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

September 9, 2026

Advisory Details (5)

Auto-updated Aug 20, 2026
🔬 Proof of concept available. 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 9db091b04f56 (libevent/libevent)

Patch available: libevent/libevent release-2.2.2-alpha (contains commit 9db091b04f56)

https://github.com/libevent/libevent/commit/9db091b04f569be3a700fa9860ef02f90b830af9
github_commit Patch Available

commit 5cb95ba2f804 (libevent/libevent)

Patch available: libevent/libevent release-2.1.13-stable (contains commit 5cb95ba2f804)

https://github.com/libevent/libevent/commit/5cb95ba2f804f8aff46f88d58391c71e1251cd1c
githubMentions a patch (unverified)🟡 PoC Available

Dangling Pointer in `evbuffer_add_buffer_reference` · Advisory · libevent/libevent · GitHub

https://github.com/libevent/libevent/security/advisories/GHSA-c2pj-cg4r-88c8

Vendor Advisories for CVE-2026-63381(11)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(11)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntulibevent-pthreads-2.0-5 (2.0.21-stable-2ubuntu0.16.04.1+esm1) @ xenial2026-10-07ubuntu
redhatcert-manager/jetstack-cert-manager-rhel9:17905899122026-09-28redhat
redhatcert-manager/cert-manager-operator-rhel9:17905898552026-09-28redhat
redhatcert-manager/cert-manager-istio-csr-rhel9:17905899142026-09-28redhat
redhatcert-manager/jetstack-cert-manager-rhel9:17902232792026-09-28redhat
redhatcert-manager/cert-manager-istio-csr-rhel9:17902237192026-09-28redhat
redhatcert-manager/cert-manager-operator-rhel9:17902724262026-09-28redhat
redhatrhui5/rhua-rhel9:17902420042026-09-24redhat
redhatlibevent-0:2.1.13-1.el9_82026-09-16redhat
redhatlibevent-0:2.1.13-1.el10_22026-09-16redhat
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.

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 19× in last 7d / 71× 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 100 of 119 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. None are among the latest 100 rows. The 19 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-11 14:10 UTCEG score recompute
  2. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.2% · 4th percentile
  3. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.2% · 4th percentile
  4. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.2% · 4th percentile
  5. 2026-10-09 08:32 UTCEG score recompute
  6. 2026-10-09 08:32 UTCVendor advisory
  7. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.2% · 4th percentile
  8. 2026-10-08 07:21 UTCEG score recompute
  9. 2026-10-08 07:21 UTCVendor advisory
  10. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.2% · 4th percentile
  11. 2026-10-07 07:24 UTCEG score recompute
  12. 2026-10-07 07:24 UTCVendor advisory
  13. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.2% · 4th percentile
  14. 2026-10-06 07:52 UTCEG score recompute
  15. 2026-10-06 07:52 UTCVendor advisory
  16. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.2% · 4th percentile
  17. 2026-10-05 05:57 UTCEG score recompute
  18. 2026-10-05 05:57 UTCVendor advisory
  19. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.2% · 4th percentile
  20. 2026-10-04 06:22 UTCVendor advisory
  21. 2026-10-03 06:50 UTCEG score recompute
  22. 2026-10-03 06:50 UTCVendor advisory
  23. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.2% · 4th percentile
  24. 2026-10-02 07:17 UTCEG score recompute
  25. 2026-10-02 07:17 UTCVendor advisory
Show 75 more
  1. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.2% · 4th percentile
  2. 2026-10-01 07:45 UTCEG score recompute
  3. 2026-10-01 07:45 UTCVendor advisory
  4. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.2% · 4th percentile
  5. 2026-09-30 08:13 UTCEG score recompute
  6. 2026-09-30 08:13 UTCVendor advisory
  7. 2026-09-29 02:12 UTCEG score recompute
  8. 2026-09-29 02:12 UTCVendor advisory
  9. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.2% · 4th percentile
  10. 2026-09-28 02:39 UTCEG score recompute
  11. 2026-09-28 02:39 UTCVendor advisory
  12. 2026-09-27 03:01 UTCEG score recompute
  13. 2026-09-27 03:01 UTCVendor advisory
  14. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.2% · 4th percentile
  15. 2026-09-24 19:41 UTCEG score recompute
  16. 2026-09-24 19:41 UTCVendor advisory
  17. 2026-09-23 20:05 UTCEG score recompute
  18. 2026-09-23 20:05 UTCVendor advisory
  19. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  20. 2026-09-22 19:49 UTCEG score recompute
  21. 2026-09-22 19:49 UTCVendor advisory
  22. 2026-09-21 20:17 UTCVendor advisory
  23. 2026-09-20 20:44 UTCEG score recompute
  24. 2026-09-20 20:44 UTCVendor advisory
  25. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  26. 2026-09-19 21:12 UTCEG score recompute
  27. 2026-09-19 21:12 UTCVendor advisory
  28. 2026-09-18 21:39 UTCEG score recompute
  29. 2026-09-18 21:39 UTCVendor advisory
  30. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  31. 2026-09-17 21:19 UTCEG score recompute
  32. 2026-09-17 21:19 UTCVendor advisory
  33. 2026-09-16 20:01 UTCEG score recompute
  34. 2026-09-16 20:01 UTCVendor advisory
  35. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  36. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  37. 2026-09-15 19:52 UTCEG score recompute
  38. 2026-09-15 19:52 UTCVendor advisory
  39. 2026-09-14 20:18 UTCVendor advisory
  40. 2026-09-13 20:43 UTCEG score recompute
  41. 2026-09-13 20:43 UTCVendor advisory
  42. 2026-09-12 21:11 UTCEG score recompute
  43. 2026-09-12 21:11 UTCVendor advisory
  44. 2026-09-11 21:39 UTCEG score recompute
  45. 2026-09-11 21:39 UTCVendor advisory
  46. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  47. 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  48. 2026-09-10 22:06 UTCEG score recompute
  49. 2026-09-10 22:06 UTCVendor advisory
  50. 2026-09-09 22:34 UTCVendor advisory
  51. 2026-09-09 01:56 UTCEG score recompute
  52. 2026-09-09 01:56 UTCVendor advisory
  53. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  54. 2026-09-07 19:44 UTCEG score recompute
  55. 2026-09-07 19:44 UTCVendor advisory
  56. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  57. 2026-09-06 20:12 UTCEG score recompute
  58. 2026-09-06 20:12 UTCVendor advisory
  59. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  60. 2026-09-05 20:39 UTCEG score recompute
  61. 2026-09-05 20:39 UTCVendor advisory
  62. 2026-09-05 15:31 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  63. 2026-09-04 21:07 UTCEG score recompute
  64. 2026-09-04 21:07 UTCVendor advisory
  65. 2026-09-03 20:41 UTCVendor advisory
  66. 2026-09-02 21:09 UTCEG score recompute
  67. 2026-09-02 21:09 UTCVendor advisory
  68. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  69. 2026-09-01 18:39 UTCEG score recompute
  70. 2026-09-01 18:39 UTCVendor advisory
  71. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  72. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  73. 2026-08-31 19:04 UTCEG score recompute
  74. 2026-08-31 19:04 UTCVendor advisory
  75. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.1% · 2nd percentile

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Frequently asked(5)

What is CVE-2026-63381?
CVE-2026-63381 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 has a use-after-free in buffer.c when evbufferaddbufferreference processes an output buffer whose outtotallen is zero. evbufferfreeallchains frees the initial empty chain without resetting outbuf->first,…
When was the CVE record for CVE-2026-63381 published?
The CVE record for CVE-2026-63381 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 September 9, 2026; the record at its source may have been updated since.
Is CVE-2026-63381 actively exploited?
CVE-2026-63381 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (4th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-63381?
CVE-2026-63381 has a CVSS base score of 5.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-63381?
A fix for CVE-2026-63381 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-63381 are linked in the Vendor Advisories panel on this page.

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