CVE-2026-63383

HIGHPre-NVD 8.78.7—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.7 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 68% 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
Trending — Patch released this weekElevated
8.7EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.7Exploit: Elevated riskExposed: 0

A fix is available — apply it.

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent can read beyond a contiguous evbuffer region in event_tagging.c when decode_tag_internal requests at most five bytes from evbuffer_pullup but iterates using the full logical buffer length. A fragmented evbuffer containing a six-byte malformed tag can therefore advance past the pullup window and trigger an out-of-bounds read, which can crash a process that decodes attacker-controlled tagged RPC data. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

CVSS v3
8.7
EG Score
8.7(medium)
EG Risk
70(Attend)
EG Risk 70/100SSVC: Attend

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
Severity87% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
0%
EPSS %ILE
32%
KEV
Not listed

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_commit, github_release, github.
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 e1f9e21887c6 (libevent/libevent)

Patch available: libevent/libevent release-2.1.13-stable (contains commit e1f9e21887c6)

https://github.com/libevent/libevent/commit/e1f9e21887c6b104e206a718385ba3ffc75180cb
github_commit Patch Available

commit 91ed8745eeba (libevent/libevent)

Patch available: libevent/libevent release-2.2.2-alpha (contains commit 91ed8745eeba)

https://github.com/libevent/libevent/commit/91ed8745eebabdd27592a83d350338a8c4626321
github Patch Available🟡 PoC Available

decode_tag_internal() can lead to out-of-bounds read · Advisory · libevent/libevent · GitHub

https://github.com/libevent/libevent/security/advisories/GHSA-fj29-64w6-73h6

Vendor Advisories for CVE-2026-63383(1)

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

Patch Availability(5)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulibevent-pthreads-2.1-7t64 (2.1.12-stable-9ubuntu2.1) @ noble2026-09-19ubuntu
redhatlibevent-0:2.1.13-1.el10_22026-09-16redhat
redhatlibevent-0:2.1.8-11.el8_102026-09-16redhat
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 rangeFixed inDependents
libevent2.1.12-stable-10 ... 2.1.13-stable-1 (7 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
libevent2.1.12-stable-10, 2.1.13-stable-1——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
libevent2.1.12-stable-102.1.13-stable-1—

Weakness Classification(1)

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

Additional Vendor Advisories

(4)

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 23× in last 7d / 87× 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.

  1. 2026-09-19 14:18 UTCVendor advisory
  2. 2026-09-19 01:24 UTCEG score recompute
  3. 2026-09-19 01:24 UTCVendor advisory
  4. 2026-09-18 19:28 UTCEPSS rescore
  5. 2026-09-18 12:46 UTCVendor advisory
  6. 2026-09-18 00:08 UTCEG score recompute
  7. 2026-09-18 00:08 UTCVendor advisory
  8. 2026-09-17 11:31 UTCVendor advisory
  9. 2026-09-16 22:42 UTCEG score recompute
  10. 2026-09-16 22:42 UTCVendor advisory
  11. 2026-09-16 14:08 UTCEPSS rescore
  12. 2026-09-16 09:46 UTCEG score recompute
  13. 2026-09-16 09:46 UTCVendor advisory
  14. 2026-09-16 05:15 UTCEPSS rescore
  15. 2026-09-15 21:08 UTCVendor advisory
  16. 2026-09-15 07:46 UTCEG score recompute
  17. 2026-09-15 07:46 UTCVendor advisory
  18. 2026-09-14 19:08 UTCVendor advisory
  19. 2026-09-14 04:45 UTCEG score recompute
  20. 2026-09-14 04:45 UTCVendor advisory
  21. 2026-09-13 16:07 UTCVendor advisory
  22. 2026-09-13 03:29 UTCEG score recompute
  23. 2026-09-13 03:29 UTCVendor advisory
  24. 2026-09-12 14:51 UTCVendor advisory
  25. 2026-09-12 02:13 UTCEG score recompute
Show 67 more
  1. 2026-09-12 02:13 UTCVendor advisory
  2. 2026-09-11 14:53 UTCEPSS rescore
  3. 2026-09-11 13:34 UTCEG score recompute
  4. 2026-09-11 13:34 UTCVendor advisory
  5. 2026-09-11 09:37 UTCEPSS rescore
  6. 2026-09-11 00:54 UTCVendor advisory
  7. 2026-09-10 12:16 UTCEG score recompute
  8. 2026-09-10 12:16 UTCVendor advisory
  9. 2026-09-09 22:34 UTCVendor advisory
  10. 2026-09-09 14:34 UTCVendor advisory
  11. 2026-09-09 01:56 UTCEG score recompute
  12. 2026-09-09 01:56 UTCVendor advisory
  13. 2026-09-08 22:01 UTCEPSS rescore
  14. 2026-09-08 07:09 UTCVendor advisory
  15. 2026-09-07 18:32 UTCEG score recompute
  16. 2026-09-07 18:32 UTCVendor advisory
  17. 2026-09-07 16:01 UTCEPSS rescore
  18. 2026-09-07 05:54 UTCVendor advisory
  19. 2026-09-06 17:17 UTCEG score recompute
  20. 2026-09-06 17:17 UTCVendor advisory
  21. 2026-09-06 13:47 UTCEPSS rescore
  22. 2026-09-06 04:39 UTCVendor advisory
  23. 2026-09-05 16:01 UTCEG score recompute
  24. 2026-09-05 16:01 UTCVendor advisory
  25. 2026-09-05 15:31 UTCEPSS rescore
  26. 2026-09-05 03:21 UTCVendor advisory
  27. 2026-09-04 14:43 UTCEG score recompute
  28. 2026-09-04 14:43 UTCVendor advisory
  29. 2026-09-04 05:07 UTCEPSS rescore
  30. 2026-09-04 02:03 UTCVendor advisory
  31. 2026-09-03 13:26 UTCVendor advisory
  32. 2026-09-03 00:42 UTCEG score recompute
  33. 2026-09-03 00:42 UTCVendor advisory
  34. 2026-09-02 14:12 UTCEPSS rescore
  35. 2026-09-02 12:04 UTCVendor advisory
  36. 2026-09-01 23:22 UTCEG score recompute
  37. 2026-09-01 23:22 UTCVendor advisory
  38. 2026-09-01 13:54 UTCEPSS rescore
  39. 2026-09-01 10:44 UTCEG score recompute
  40. 2026-09-01 10:44 UTCVendor advisory
  41. 2026-09-01 04:40 UTCEPSS rescore
  42. 2026-08-31 22:05 UTCVendor advisory
  43. 2026-08-31 09:26 UTCVendor advisory
  44. 2026-08-30 20:40 UTCEG score recompute
  45. 2026-08-30 20:40 UTCVendor advisory
  46. 2026-08-30 19:17 UTCEPSS rescore
  47. 2026-08-30 08:02 UTCEG score recompute
  48. 2026-08-30 01:22 UTCEPSS rescore
  49. 2026-08-29 06:44 UTCEG score recompute
  50. 2026-08-28 21:42 UTCEPSS rescore
  51. 2026-08-27 15:36 UTCEG score recompute
  52. 2026-08-27 14:25 UTCEPSS rescore
  53. 2026-08-27 02:54 UTCEG score recompute
  54. 2026-08-26 14:46 UTCEPSS rescore
  55. 2026-08-26 01:38 UTCEG score recompute
  56. 2026-08-25 13:49 UTCEPSS rescore
  57. 2026-08-25 00:22 UTCEG score recompute
  58. 2026-08-24 11:43 UTCEG score recompute
  59. 2026-08-23 10:27 UTCEG score recompute
  60. 2026-08-23 00:19 UTCEPSS rescore
  61. 2026-08-22 09:12 UTCEG score recompute
  62. 2026-08-21 23:49 UTCEPSS rescore
  63. 2026-08-20 19:18 UTCEG score recompute
  64. 2026-08-20 18:52 UTCEG score recompute
  65. 2026-08-20 18:17 UTCEG score recompute
  66. 2026-08-20 17:57 UTCEG score recompute
  67. 2026-08-20 17:56 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-63383?
CVE-2026-63383 is a high vulnerability published on August 20, 2026. Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent can read beyond a contiguous evbuffer region in eventtagging.c when decodetaginternal requests at most five bytes from evbufferpullup but iterates using the full logical buffer length. A fragmented evbuffer…
When was CVE-2026-63383 disclosed?
CVE-2026-63383 was first published in the National Vulnerability Database on August 20, 2026, with the most recent update on September 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-63383 actively exploited?
CVE-2026-63383 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 67.7% of all scored CVEs.
What is the CVSS score of CVE-2026-63383?
CVE-2026-63383 has a CVSS v3 base score of 8.7 (NVD).
How do I remediate CVE-2026-63383?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-63383, 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

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