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% (33rd 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 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: 0.4%CVSS: 7.0Exploit: Elevated riskExposed 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 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
7.0HIGHmedium confidence
EG Risk
48
EG Risk 48/100CISA SSVC

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%
CISA SSVC: Track at low or medium mission impact; Track* at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.4%
EPSS %ILE
33rd
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track* at high (mission-essential systems).

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

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

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
githubMentions a patch (unverified)🟡 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(12)

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

Patch Availability(12)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntulibevent-pthreads-2.0-5 (2.0.21-stable-2ubuntu0.16.04.1+esm2) @ xenial2026-10-07ubuntu
redhatcert-manager/cert-manager-istio-csr-rhel9:17902237192026-09-28redhat
redhatcert-manager/jetstack-cert-manager-rhel9:17905899122026-09-28redhat
redhatcert-manager/jetstack-cert-manager-rhel9:17902232792026-09-28redhat
redhatcert-manager/cert-manager-istio-csr-rhel9:17905899142026-09-28redhat
redhatcert-manager/cert-manager-operator-rhel9:17905898552026-09-28redhat
redhatcert-manager/cert-manager-operator-rhel9:17902724262026-09-28redhat
redhatrhui5/rhua-rhel9:17902420042026-09-24redhat
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-2.1.13-0.1.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 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(3)

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 26× in last 7d / 99× 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.

Showing the most recent 100 of 146 total refreshes for this CVE.

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

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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 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 0.4% probability of exploitation in the next 30 days (33rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-63387?
CVE-2026-63387 has a CVSS base score of 7.0 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-63387?
A fix for CVE-2026-63387 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-63387 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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