CVE-2026-63388

HIGHPre-NVD 8.48.4
EchelonGraph scoreMEDIUM confidence

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

This high-severity CVE scores 8.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.1% (3rd 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-2026-63501 (ENISA EUVD)Source: ENISA EUVD

8.4EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.1%CVSS: 8.4Exploit: 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 heap out-of-bounds write in bufferevent_sock.c when bufferevent_socket_set_conn_address_ copies a kernel-supplied AF_UNIX peer address into bufferevent_private.conn_address. Release builds compiled with NDEBUG disable the EVUTIL_ASSERT length guard, and the evhttp accept path can pass a 110-byte sockaddr from accept() into the 28-byte field. An unauthenticated local peer able to connect to an AF_UNIX listener can overwrite the adjacent dns_request pointer and heap data, causing memory corruption with confidentiality, integrity, and availability impact. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

CVSS v3
8.4
EG Score
8.4HIGHmedium confidence
EG Risk
38
EG Risk 38/100

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)
Severity84% × 45%
Impact severity (EG Severity): CVSS 8.4 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.1% × 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 low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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
0.1%
EPSS %ILE
3rd
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 (8.4): severity, escalated by confirmed exploitation. This CVE's 8.4 is its impact severity (EG Severity), not escalated.

EG Severity
8.4 HIGHCVSS-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
0.1% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-25). 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; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade 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; Track* at high (mission-essential systems).

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

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (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 ef38f926e9cd (libevent/libevent)

Patch available: libevent/libevent release-2.1.13-stable (contains commit ef38f926e9cd)

https://github.com/libevent/libevent/commit/ef38f926e9cd1f082416c6fff13587bc1f431d72
GitHub commit Patch Available

commit 52057cb33d0c (libevent/libevent)

Patch available: libevent/libevent release-2.2.2-alpha (contains commit 52057cb33d0c)

https://github.com/libevent/libevent/commit/52057cb33d0c20c0a0453fbabe6c0c96854931b9
GitHub advisoryMentions a patch (unverified)

Heap out-of-bounds write in bufferevent_socket_set_conn_address_ reachable via AF_UNIX accept · Advisory · libevent/libevent · GitHub

https://github.com/libevent/libevent/security/advisories/GHSA-cvq5-vrvr-j338

Vendor Advisories for CVE-2026-63388(13)

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) @ xenial2026-10-26ubuntu
redhatcert-manager/jetstack-cert-manager-rhel9:17905899122026-09-28redhat
redhatcert-manager/cert-manager-operator-rhel9:17905898552026-09-28redhat
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
redhatcert-manager/cert-manager-istio-csr-rhel9:17905899142026-09-28redhat
redhatrhui5/rhua-rhel9:17902420042026-09-24redhat
redhatlibevent-0:2.1.8-11.el8_102026-09-16redhat
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(2)

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 9× in last 7d / 56× 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 192 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 92 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 0.1% · 3rd percentile
  2. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  3. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  4. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  5. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  6. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  7. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  8. 2026-10-26 10:26 UTCEG score recompute
  9. 2026-10-26 10:26 UTCVendor advisory
  10. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  11. 2026-10-25 14:13 UTCEG score recompute
  12. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  13. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  14. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  15. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  16. 2026-10-20 18:52 UTCEG score recompute
  17. 2026-10-20 18:52 UTCVendor advisory
  18. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  19. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  20. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  21. 2026-10-18 03:23 UTCEG score recompute
  22. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  23. 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  24. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  25. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
Show 75 more
  1. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  2. 2026-10-13 12:00 UTCEG score recompute
  3. 2026-10-13 12:00 UTCVendor advisory
  4. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.1% · 3rd 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 0.1% · 3rd percentile
  10. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  11. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  12. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  13. 2026-10-08 05:22 UTCEG score recompute
  14. 2026-10-08 05:22 UTCVendor advisory
  15. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  16. 2026-10-07 06:37 UTCVendor advisory
  17. 2026-10-06 19:22 UTCEG score recompute
  18. 2026-10-06 19:22 UTCVendor advisory
  19. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  20. 2026-10-06 07:52 UTCVendor advisory
  21. 2026-10-05 19:28 UTCEG score recompute
  22. 2026-10-05 19:28 UTCVendor advisory
  23. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  24. 2026-10-05 08:06 UTCEG score recompute
  25. 2026-10-05 08:06 UTCVendor advisory
  26. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  27. 2026-10-04 20:52 UTCVendor advisory
  28. 2026-10-04 06:37 UTCVendor advisory
  29. 2026-10-03 19:24 UTCEG score recompute
  30. 2026-10-03 19:24 UTCVendor advisory
  31. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  32. 2026-10-03 07:12 UTCVendor advisory
  33. 2026-10-02 19:56 UTCEG score recompute
  34. 2026-10-02 19:56 UTCVendor advisory
  35. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.1% · 2nd percentile
  36. 2026-10-02 08:42 UTCVendor advisory
  37. 2026-10-01 21:29 UTCEG score recompute
  38. 2026-10-01 21:29 UTCVendor advisory
  39. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  40. 2026-10-01 07:44 UTCVendor advisory
  41. 2026-09-30 20:31 UTCEG score recompute
  42. 2026-09-30 20:31 UTCVendor advisory
  43. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  44. 2026-09-30 08:13 UTCEG score recompute
  45. 2026-09-30 08:13 UTCVendor advisory
  46. 2026-09-29 01:55 UTCEG score recompute
  47. 2026-09-29 01:55 UTCVendor advisory
  48. 2026-09-28 14:37 UTCEG score recompute
  49. 2026-09-28 14:37 UTCVendor advisory
  50. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  51. 2026-09-28 03:10 UTCVendor advisory
  52. 2026-09-27 15:57 UTCEG score recompute
  53. 2026-09-27 15:57 UTCVendor advisory
  54. 2026-09-27 03:01 UTCEG score recompute
  55. 2026-09-27 03:01 UTCVendor advisory
  56. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.2% · 8th percentile
  57. 2026-09-25 06:20 UTCVendor advisory
  58. 2026-09-24 19:06 UTCEG score recompute
  59. 2026-09-24 19:06 UTCVendor advisory
  60. 2026-09-24 07:19 UTCVendor advisory
  61. 2026-09-23 20:05 UTCEG score recompute
  62. 2026-09-23 20:05 UTCVendor advisory
  63. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  64. 2026-09-23 06:59 UTCVendor advisory
  65. 2026-09-22 19:45 UTCEG score recompute
  66. 2026-09-22 19:45 UTCVendor advisory
  67. 2026-09-22 06:17 UTCEG score recompute
  68. 2026-09-22 06:17 UTCVendor advisory
  69. 2026-09-21 19:04 UTCVendor advisory
  70. 2026-09-21 07:49 UTCEG score recompute
  71. 2026-09-21 07:49 UTCVendor advisory
  72. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  73. 2026-09-20 20:14 UTCVendor advisory
  74. 2026-09-20 09:00 UTCVendor advisory
  75. 2026-09-19 20:18 UTCEG score recompute

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Frequently asked(5)

What is CVE-2026-63388?
CVE-2026-63388 is a high-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 heap out-of-bounds write in bufferevent_sock.c when bufferevent_socket_set_conn_address_ copies a kernel-supplied AF_UNIX peer address into bufferevent_private.conn_address. Release builds compiled with…
When was the CVE record for CVE-2026-63388 published?
The CVE record for CVE-2026-63388 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-2026-63388 actively exploited?
CVE-2026-63388 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.1% probability of exploitation in the next 30 days (3rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-63388?
CVE-2026-63388 has a CVSS base score of 8.4 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-63388?
A fix for CVE-2026-63388 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-63388 are linked in the Vendor Advisories panel on this page.

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