CVE-2026-34876

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-04-02. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.5Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

An issue was discovered in Mbed TLS 3.x before 3.6.6. An out-of-bounds read vulnerability in mbedtls_ccm_finish() in library/ccm.c allows attackers to obtain adjacent CCM context data via invocation of the multipart CCM API with an oversized tag_len parameter. This is caused by missing validation of the tag_len parameter against the size of the internal 16-byte authentication buffer. The issue affects the public multipart CCM API in Mbed TLS 3.x, where mbedtls_ccm_finish() can be invoked directly by applications. In Mbed TLS 4.x versions prior to the fix, the same missing validation exists in the internal implementation; however, the function is not exposed as part of the public API. Exploitation requires application-level invocation of the multipart CCM API.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: 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
Severity75% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
33%
KEV
Not listed

Published

April 2, 2026

Last Modified

July 24, 2026

Advisory Details (2)

Auto-updated Jun 10, 2026
No patch confirmed yet.
generic

Security Advisories — Mbed TLS documentation

https://mbed-tls.readthedocs.io/en/latest/tech-updates/security-advisories/
generic

CCM multipart finish tag-length validation bypass (CVE-2026-34876) — Mbed TLS documentation

https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ccm-finish-boundary-check/

Vendor Advisories for CVE-2026-34876(1)

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

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFixed inDependents
mbedtls2.28.3-1 ... 3.6.7-3 (22 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
mbedtls3.6.4-2 ... 3.6.7-3 (6 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
mbedtls3.6.4-2, 3.6.5-0.1, 3.6.5-0.1~deb13u13.6.6-0.1—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 7× in last 7d / 29× 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 187 total refreshes for this CVE.

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

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-34876?
CVE-2026-34876 is a high vulnerability published on April 2, 2026. An issue was discovered in Mbed TLS 3.x before 3.6.6. An out-of-bounds read vulnerability in mbedtlsccmfinish() in library/ccm.c allows attackers to obtain adjacent CCM context data via invocation of the multipart CCM API with an oversized taglen parameter. This is caused by missing validation of…
When was CVE-2026-34876 disclosed?
CVE-2026-34876 was first published in the National Vulnerability Database on April 2, 2026, with the most recent update on July 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-34876 actively exploited?
CVE-2026-34876 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 67.4% of all scored CVEs.
What is the CVSS score of CVE-2026-34876?
CVE-2026-34876 has a CVSS v3.1 base score of 7.5 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-34876?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-34876, 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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