CVE-2026-63387

HIGHPre-NVD 7.07.0—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.0 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 64% 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
7.0EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.0Exploit: 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 has an off-by-one stack buffer overflow in evdns.c when dnsname_to_labels formats a name-bearing DNS record at the end of the 64 KB stack buffer allocated by evdns_server_request_format_response. The final-label check permits j plus label_len plus one to equal buf_len, after which the terminating null byte is written to buf[buf_len]. A crafted DNS server response containing PTR, CNAME, MX, NS, or SOA data can trigger the one-byte out-of-bounds write and crash or corrupt the process. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

CVSS v3
7.0
EG Score
7.0(medium)
EG Risk
48(Track)
EG Risk 48/100SSVC: 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 computed
Severity70% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
36%
KEV
Not listed

Published

August 20, 2026

Last Modified

September 9, 2026

Advisory Details (3)

Auto-updated Aug 20, 2026
🔬 Proof of concept available. Patch available. Sources: github, 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 Patch Available🟡 PoC Available

Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response · Advisory · libevent/libevent · GitHub

https://github.com/libevent/libevent/security/advisories/GHSA-58rx-7448-jw47

Vendor Advisories for CVE-2026-63387(1)

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

Patch Availability(4)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatlibevent-0:2.1.13-1.el10_22026-09-16redhat
redhatlibevent-0:2.1.13-1.el9_82026-09-16redhat
redhatlibevent-0:2.1.8-11.el8_102026-09-16redhat
redhatlibevent-main-2.1.13-0.1.hum12026-09-03redhat

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(3)

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

Additional Vendor Advisories

(3)

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 / 79× 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 04:16 UTCEG score recompute
  2. 2026-09-19 04:16 UTCVendor advisory
  3. 2026-09-18 19:28 UTCEPSS rescore
  4. 2026-09-18 15:17 UTCVendor advisory
  5. 2026-09-18 02:17 UTCEG score recompute
  6. 2026-09-18 02:17 UTCVendor advisory
  7. 2026-09-17 13:17 UTCVendor advisory
  8. 2026-09-17 00:17 UTCEG score recompute
  9. 2026-09-17 00:17 UTCVendor advisory
  10. 2026-09-16 14:08 UTCEPSS rescore
  11. 2026-09-16 11:18 UTCEG score recompute
  12. 2026-09-16 11:18 UTCVendor advisory
  13. 2026-09-16 05:15 UTCEPSS rescore
  14. 2026-09-15 22:18 UTCVendor advisory
  15. 2026-09-15 09:18 UTCEG score recompute
  16. 2026-09-15 09:18 UTCVendor advisory
  17. 2026-09-14 20:18 UTCVendor advisory
  18. 2026-09-14 07:14 UTCVendor advisory
  19. 2026-09-13 18:15 UTCEG score recompute
  20. 2026-09-13 18:15 UTCVendor advisory
  21. 2026-09-13 05:15 UTCVendor advisory
  22. 2026-09-12 16:15 UTCEG score recompute
  23. 2026-09-12 16:15 UTCVendor advisory
  24. 2026-09-12 03:16 UTCEG score recompute
  25. 2026-09-12 03:16 UTCVendor advisory
Show 54 more
  1. 2026-09-11 14:53 UTCEPSS rescore
  2. 2026-09-11 14:16 UTCEG score recompute
  3. 2026-09-11 14:16 UTCVendor advisory
  4. 2026-09-11 09:37 UTCEPSS rescore
  5. 2026-09-11 01:16 UTCVendor advisory
  6. 2026-09-10 12:16 UTCEG score recompute
  7. 2026-09-10 12:16 UTCVendor advisory
  8. 2026-09-09 22:34 UTCVendor advisory
  9. 2026-09-09 14:56 UTCVendor advisory
  10. 2026-09-09 01:56 UTCEG score recompute
  11. 2026-09-09 01:56 UTCVendor advisory
  12. 2026-09-08 22:01 UTCEPSS rescore
  13. 2026-09-07 20:24 UTCEG score recompute
  14. 2026-09-07 20:24 UTCVendor advisory
  15. 2026-09-07 16:01 UTCEPSS rescore
  16. 2026-09-07 07:24 UTCVendor advisory
  17. 2026-09-06 18:19 UTCEG score recompute
  18. 2026-09-06 18:19 UTCVendor advisory
  19. 2026-09-06 13:47 UTCEPSS rescore
  20. 2026-09-06 05:19 UTCVendor advisory
  21. 2026-09-05 16:19 UTCEG score recompute
  22. 2026-09-05 16:19 UTCVendor advisory
  23. 2026-09-05 15:31 UTCEPSS rescore
  24. 2026-09-05 03:18 UTCVendor advisory
  25. 2026-09-04 14:17 UTCEG score recompute
  26. 2026-09-04 05:07 UTCEPSS rescore
  27. 2026-09-02 23:15 UTCEG score recompute
  28. 2026-09-02 14:12 UTCEPSS rescore
  29. 2026-09-01 21:16 UTCEG score recompute
  30. 2026-09-01 13:54 UTCEPSS rescore
  31. 2026-09-01 08:17 UTCEG score recompute
  32. 2026-09-01 04:40 UTCEPSS rescore
  33. 2026-08-31 05:28 UTCEG score recompute
  34. 2026-08-30 19:17 UTCEPSS rescore
  35. 2026-08-30 03:28 UTCEG score recompute
  36. 2026-08-30 01:22 UTCEPSS rescore
  37. 2026-08-29 01:28 UTCEG score recompute
  38. 2026-08-28 21:42 UTCEPSS rescore
  39. 2026-08-27 20:34 UTCEG score recompute
  40. 2026-08-27 14:25 UTCEPSS rescore
  41. 2026-08-26 18:26 UTCEG score recompute
  42. 2026-08-26 14:46 UTCEPSS rescore
  43. 2026-08-25 16:26 UTCEG score recompute
  44. 2026-08-25 15:16 UTCEG score recompute
  45. 2026-08-25 13:49 UTCEPSS rescore
  46. 2026-08-25 02:15 UTCEG score recompute
  47. 2026-08-24 13:15 UTCEG score recompute
  48. 2026-08-23 11:16 UTCEG score recompute
  49. 2026-08-23 00:19 UTCEPSS rescore
  50. 2026-08-22 09:17 UTCEG score recompute
  51. 2026-08-21 23:49 UTCEPSS rescore
  52. 2026-08-20 18:17 UTCEG score recompute
  53. 2026-08-20 17:57 UTCEG score recompute
  54. 2026-08-20 17:56 UTCMITRE cvelistV5first tracked

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-63387?
CVE-2026-63387 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 has an off-by-one stack buffer overflow in evdns.c when dnsnametolabels formats a name-bearing DNS record at the end of the 64 KB stack buffer allocated by evdnsserverrequestformatresponse. The final-label check…
When was CVE-2026-63387 disclosed?
CVE-2026-63387 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-2026-63387 actively exploited?
CVE-2026-63387 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 64.5% of all scored CVEs.
What is the CVSS score of CVE-2026-63387?
CVE-2026-63387 has a CVSS v3 base score of 7.0 (NVD).
How do I remediate CVE-2026-63387?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-63387, 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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