CVE-2026-63383

HIGHPre-NVD 8.78.7
EchelonGraph scoreMEDIUM confidence

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

This high-severity CVE scores 8.7 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (40th 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 weekElevated
8.7EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 8.7Exploit: No code on recordExposed 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 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
8.7HIGHmedium confidence
EG Risk
70
EG Risk 70/100

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)
Severity87% × 45%
The EG Score, 8.7 of 10.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable yes (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 at low or medium mission impact and sooner than that at high.
EPSS PROB
0.5%
EPSS %ILE
40th
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable yes (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)14 days if the affected system is publicly exposed; 60 days if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable yes (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
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 advisoryMentions a patch (unverified)

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(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-2.1-7 (2.1.11-stable-1ubuntu0.1~esm1) @ focal2026-10-13ubuntu
redhatcert-manager/cert-manager-istio-csr-rhel9:17905899142026-09-28redhat
redhatcert-manager/cert-manager-operator-rhel9:17905898552026-09-28redhat
redhatcert-manager/jetstack-cert-manager-rhel9:17905899122026-09-28redhat
redhatcert-manager/cert-manager-istio-csr-rhel9:17902237192026-09-28redhat
redhatcert-manager/cert-manager-operator-rhel9:17902724262026-09-28redhat
redhatcert-manager/jetstack-cert-manager-rhel9:17902232792026-09-28redhat
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-0:2.1.8-11.el8_102026-09-16redhat
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 15× in last 7d / 90× 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 164 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 64 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.5% · 40th 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 0.5% · 40th 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 0.5% · 40th percentile
  10. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  11. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  12. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.5% · 40th 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 0.5% · 42nd percentile
  16. 2026-10-07 05:30 UTCVendor advisory
  17. 2026-10-06 16:53 UTCEG score recompute
  18. 2026-10-06 16:53 UTCVendor advisory
  19. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  20. 2026-10-06 03:25 UTCVendor advisory
  21. 2026-10-06 03:24 UTCVendor advisory
  22. 2026-10-06 03:24 UTCEG score recompute
  23. 2026-10-06 03:24 UTCVendor advisory
  24. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  25. 2026-10-05 09:30 UTCEG score recompute
Show 75 more
  1. 2026-10-05 09:30 UTCVendor advisory
  2. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  3. 2026-10-04 20:52 UTCVendor advisory
  4. 2026-10-04 05:24 UTCVendor advisory
  5. 2026-10-03 16:47 UTCEG score recompute
  6. 2026-10-03 16:47 UTCVendor advisory
  7. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  8. 2026-10-03 01:36 UTCEG score recompute
  9. 2026-10-03 01:36 UTCVendor advisory
  10. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  11. 2026-10-02 12:55 UTCVendor advisory
  12. 2026-10-01 22:44 UTCEG score recompute
  13. 2026-10-01 22:44 UTCVendor advisory
  14. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  15. 2026-10-01 09:30 UTCVendor advisory
  16. 2026-09-30 20:51 UTCEG score recompute
  17. 2026-09-30 20:51 UTCVendor advisory
  18. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  19. 2026-09-30 08:13 UTCEG score recompute
  20. 2026-09-30 08:13 UTCVendor advisory
  21. 2026-09-28 21:38 UTCEG score recompute
  22. 2026-09-28 21:38 UTCVendor advisory
  23. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  24. 2026-09-28 04:36 UTCVendor advisory
  25. 2026-09-27 15:57 UTCEG score recompute
  26. 2026-09-27 15:57 UTCVendor advisory
  27. 2026-09-27 03:01 UTCEG score recompute
  28. 2026-09-27 03:01 UTCVendor advisory
  29. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  30. 2026-09-25 00:41 UTCEG score recompute
  31. 2026-09-25 00:41 UTCVendor advisory
  32. 2026-09-24 09:39 UTCVendor advisory
  33. 2026-09-23 21:01 UTCEG score recompute
  34. 2026-09-23 21:01 UTCVendor advisory
  35. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  36. 2026-09-23 08:23 UTCVendor advisory
  37. 2026-09-22 19:45 UTCEG score recompute
  38. 2026-09-22 19:45 UTCVendor advisory
  39. 2026-09-22 06:31 UTCEG score recompute
  40. 2026-09-22 06:31 UTCVendor advisory
  41. 2026-09-21 17:53 UTCVendor advisory
  42. 2026-09-21 04:13 UTCEG score recompute
  43. 2026-09-21 04:13 UTCVendor advisory
  44. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  45. 2026-09-20 15:34 UTCVendor advisory
  46. 2026-09-20 02:57 UTCEG score recompute
  47. 2026-09-20 02:57 UTCVendor advisory
  48. 2026-09-19 14:18 UTCVendor advisory
  49. 2026-09-19 01:24 UTCEG score recompute
  50. 2026-09-19 01:24 UTCVendor advisory
  51. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  52. 2026-09-18 12:46 UTCVendor advisory
  53. 2026-09-18 00:08 UTCEG score recompute
  54. 2026-09-18 00:08 UTCVendor advisory
  55. 2026-09-17 11:31 UTCVendor advisory
  56. 2026-09-16 22:42 UTCEG score recompute
  57. 2026-09-16 22:42 UTCVendor advisory
  58. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  59. 2026-09-16 09:46 UTCEG score recompute
  60. 2026-09-16 09:46 UTCVendor advisory
  61. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  62. 2026-09-15 21:08 UTCVendor advisory
  63. 2026-09-15 07:46 UTCEG score recompute
  64. 2026-09-15 07:46 UTCVendor advisory
  65. 2026-09-14 19:08 UTCVendor advisory
  66. 2026-09-14 04:45 UTCEG score recompute
  67. 2026-09-14 04:45 UTCVendor advisory
  68. 2026-09-13 16:07 UTCVendor advisory
  69. 2026-09-13 03:29 UTCEG score recompute
  70. 2026-09-13 03:29 UTCVendor advisory
  71. 2026-09-12 14:51 UTCVendor advisory
  72. 2026-09-12 02:13 UTCEG score recompute
  73. 2026-09-12 02:13 UTCVendor advisory
  74. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  75. 2026-09-11 13:34 UTCEG score recompute

Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-63383?
CVE-2026-63383 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 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 the CVE record for CVE-2026-63383 published?
The CVE record for CVE-2026-63383 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-2026-63383 actively exploited?
CVE-2026-63383 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (40th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-63383?
CVE-2026-63383 has a CVSS base score of 8.7 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-63383?
A fix for CVE-2026-63383 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-63383 are linked in the Vendor Advisories panel on this page.

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