CVE-2026-34873

CRITICALPre-NVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

Score 9.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-04-01. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 9.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.1Exploit: 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 3.5.0 through 4.0.0. Client impersonation can occur while resuming a TLS 1.3 session.

CVSS v3
9.1
EG Score
9.1(medium)
EG Risk
56(Track)
EG Risk 56/100SSVC: 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
Severity91% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
15%
KEV
Not listed

Published

April 1, 2026

Last Modified

June 5, 2026

Advisory Details (2)

Auto-updated Aug 1, 2026
No patch confirmed yet.
generic

Client impersonation while resuming a TLS 1.3 session (CVE-2026-34873) — Mbed TLS documentation

https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-client-impersonation-while-resuming-tls13-session/
generic

Security Advisories — Mbed TLS documentation

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

Vendor Advisories for CVE-2026-34873(1)

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

Affected Packages

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
mbedtls2.16.11-0.1 ... 3.6.7-3 (37 versions)——
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 6× in last 7d / 27× 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 216 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. 2026-09-10 09:34 UTCEPSS rescore
  6. 2026-09-08 22:00 UTCEPSS rescore
  7. 2026-09-07 16:01 UTCEPSS rescore
  8. 2026-09-06 13:47 UTCEPSS rescore
  9. 2026-09-04 05:06 UTCEPSS rescore
  10. 2026-09-02 14:12 UTCEPSS rescore
  11. 2026-09-02 11:44 UTCOSV refresh
  12. 2026-09-01 13:53 UTCEPSS rescore
  13. 2026-09-01 04:39 UTCEPSS rescore
  14. 2026-08-30 19:17 UTCEPSS rescore
  15. 2026-08-30 01:22 UTCEPSS rescore
  16. 2026-08-28 21:41 UTCEPSS rescore
  17. 2026-08-26 14:46 UTCEPSS rescore
  18. 2026-08-25 13:49 UTCEPSS rescore
  19. 2026-08-23 00:19 UTCEPSS rescore
  20. 2026-08-21 23:49 UTCEPSS rescore
  21. 2026-08-20 22:55 UTCEPSS rescore
  22. 2026-08-19 17:03 UTCEPSS rescore
  23. 2026-08-18 13:48 UTCEPSS rescore
  24. 2026-08-17 13:47 UTCEPSS rescore
  25. 2026-08-16 14:56 UTCEPSS rescore
Show 75 more
  1. 2026-08-16 09:28 UTCEG score recompute
  2. 2026-08-16 09:28 UTCGHSA enrichment
  3. 2026-08-16 02:14 UTCEPSS rescore
  4. 2026-08-15 01:30 UTCEPSS rescore
  5. 2026-08-14 22:54 UTCGHSA enrichment
  6. 2026-08-14 19:01 UTCGHSA enrichment
  7. 2026-08-14 13:39 UTCGHSA enrichment
  8. 2026-08-14 09:46 UTCGHSA enrichment
  9. 2026-08-14 05:53 UTCEG score recompute
  10. 2026-08-14 05:53 UTCGHSA enrichment
  11. 2026-08-13 22:00 UTCEPSS rescore
  12. 2026-08-13 10:05 UTCGHSA enrichment
  13. 2026-08-13 03:55 UTCGHSA enrichment
  14. 2026-08-13 00:03 UTCGHSA enrichment
  15. 2026-08-12 20:10 UTCEG score recompute
  16. 2026-08-12 20:10 UTCGHSA enrichment
  17. 2026-08-12 13:50 UTCEPSS rescore
  18. 2026-08-12 00:41 UTCGHSA enrichment
  19. 2026-08-11 20:32 UTCEG score recompute
  20. 2026-08-11 20:32 UTCGHSA enrichment
  21. 2026-08-11 07:25 UTCGHSA enrichment
  22. 2026-08-11 03:32 UTCEG score recompute
  23. 2026-08-11 03:32 UTCGHSA enrichment
  24. 2026-08-11 00:00 UTCEPSS rescore
  25. 2026-08-10 12:17 UTCGHSA enrichment
  26. 2026-08-10 08:23 UTCGHSA enrichment
  27. 2026-08-10 04:31 UTCGHSA enrichment
  28. 2026-08-10 00:38 UTCGHSA enrichment
  29. 2026-08-09 20:45 UTCGHSA enrichment
  30. 2026-08-09 16:52 UTCEG score recompute
  31. 2026-08-09 16:52 UTCGHSA enrichment
  32. 2026-08-09 13:46 UTCEPSS rescore
  33. 2026-08-09 13:00 UTCGHSA enrichment
  34. 2026-08-09 05:25 UTCEG score recompute
  35. 2026-08-09 05:25 UTCGHSA enrichment
  36. 2026-08-08 16:37 UTCEPSS rescore
  37. 2026-08-08 11:24 UTCGHSA enrichment
  38. 2026-08-08 07:04 UTCGHSA enrichment
  39. 2026-08-08 03:11 UTCGHSA enrichment
  40. 2026-08-07 23:18 UTCGHSA enrichment
  41. 2026-08-07 19:26 UTCEG score recompute
  42. 2026-08-07 19:26 UTCGHSA enrichment
  43. 2026-08-07 15:33 UTCGHSA enrichment
  44. 2026-08-06 17:59 UTCEG score recompute
  45. 2026-08-06 17:59 UTCGHSA enrichment
  46. 2026-08-06 13:46 UTCEPSS rescore
  47. 2026-08-06 08:25 UTCGHSA enrichment
  48. 2026-08-06 04:20 UTCGHSA enrichment
  49. 2026-08-06 00:28 UTCEG score recompute
  50. 2026-08-06 00:27 UTCGHSA enrichment
  51. 2026-08-05 19:17 UTCEPSS rescore
  52. 2026-08-04 15:10 UTCEPSS rescore
  53. 2026-08-04 10:38 UTCEPSS rescore
  54. 2026-08-04 02:41 UTCGHSA enrichment
  55. 2026-08-03 22:48 UTCEG score recompute
  56. 2026-08-03 22:48 UTCGHSA enrichment
  57. 2026-08-03 10:36 UTCEPSS rescore
  58. 2026-08-03 02:23 UTCGHSA enrichment
  59. 2026-08-02 22:30 UTCGHSA enrichment
  60. 2026-08-02 18:38 UTCGHSA enrichment
  61. 2026-08-02 14:45 UTCEG score recompute
  62. 2026-08-02 14:45 UTCGHSA enrichment
  63. 2026-08-02 02:27 UTCEPSS rescore
  64. 2026-08-01 04:16 UTCEPSS rescore
  65. 2026-07-30 16:28 UTCEPSS rescore
  66. 2026-07-30 01:30 UTCEPSS rescore
  67. 2026-07-27 14:13 UTCEPSS rescore
  68. 2026-07-26 14:54 UTCEPSS rescore
  69. 2026-07-26 14:54 UTCEPSS rescore
  70. 2026-07-25 14:18 UTCEPSS rescore
  71. 2026-07-25 14:18 UTCEPSS rescore
  72. 2026-07-24 14:17 UTCEPSS rescore
  73. 2026-07-24 14:17 UTCEPSS rescore
  74. 2026-07-23 14:18 UTCEPSS rescore
  75. 2026-07-23 14:18 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-34873?
CVE-2026-34873 is a critical vulnerability published on April 1, 2026. An issue was discovered in Mbed TLS 3.5.0 through 4.0.0. Client impersonation can occur while resuming a TLS 1.3 session.
When was CVE-2026-34873 disclosed?
CVE-2026-34873 was first published in the National Vulnerability Database on April 1, 2026, with the most recent update on June 5, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-34873 actively exploited?
CVE-2026-34873 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 84.7% of all scored CVEs.
What is the CVSS score of CVE-2026-34873?
CVE-2026-34873 has a CVSS v3.1 base score of 9.1 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-34873?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-34873, 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.

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