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% (42nd 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
Elevated

Also known asEUVD-2026-63502 (ENISA EUVD)Source: ENISA EUVD

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
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 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)
Severity87% × 45%
Impact severity (EG Severity): CVSS 8.7 of 10. Never the KEV-floored or EPSS-lifted EG Score.
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
42nd
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 (8.7): severity, escalated by confirmed exploitation. This CVE's 8.7 is its impact severity (EG Severity), not escalated.

EG Severity
8.7 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source
EG Likelihood
0.5% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-10). 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; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days 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; 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.

The score's inputs: 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

October 26, 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

Patch Availability(13)

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 8× in last 7d / 35× 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 its CVE.org record (CNA or CISA ADP). An arrow marks a change the record states ("CVSS → 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). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

Showing the most recent 100 of 207 rows 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 107 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

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

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 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…
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 October 26, 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 (42nd 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.

Dependency Blast Radius

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