CVE-2026-66402

CRITICALPre-NVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-08-01. a secondary CVSS source baseline 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this week
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.8Exploit: None knownExposed: 0

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

FreeRDP before 3.29.0 (affected versions <= 3.28.0) contains multiple TLS certificate identity validation weaknesses in tls_verify_certificate(), tls_match_hostname(), and x509_utils_get_dns_names(). Because FreeRDP performs custom Common Name and DNS SAN string matching instead of using OpenSSL's length-aware identity validation APIs, it (1) truncates DNS SAN values at embedded NUL bytes (accepting e.g. 'victim.example\0.attacker.example' as 'victim.example'), (2) accepts a matching Common Name even when non-matching DNS SAN entries are present, and (3) accepts IP-literal targets via DNS/CN matching without comparing iPAddress SANs. Under a trusted or misissued certificate chain, an attacker positioned to present such a certificate can bypass server identity verification, weakening TLS server authentication.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
59(Track)
EG Risk 59/100SSVC: 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
Severity98% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
21%
KEV
Not listed

Published

August 1, 2026

Last Modified

August 31, 2026

Advisory Details (3)

Auto-updated Sep 14, 2026
Patch available. Sources: github_commit, github.
generic

FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass | Advisories | VulnCheck

https://www.vulncheck.com/advisories/freerdp-before-tls-certificate-identity-validation-bypass
github Patch Available

TLS certificate identity validation accepts malformed and non-authoritative identities · Advisory · FreeRDP/FreeRDP · GitHub

https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-43hh-p3vw-hfx3
github_commit

commit b9533f07f98c (FreeRDP/FreeRDP)

Fix landed in FreeRDP/FreeRDP commit b9533f07f98c — awaiting tagged release

https://github.com/FreeRDP/FreeRDP/commit/b9533f07f98c25ed01c5f543b4d0ce73e120f5fd

Vendor Advisories for CVE-2026-66402(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
freerdp22.10.0+dfsg1-1 ... 2.9.0+dfsg1-1~bpo11+1 (32 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
freerdp22.10.0+dfsg1-1 ... 2.11.7+dfsg1-6~deb12u1 (13 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
freerdp33.15.0+dfsg-2.1 ... 3.31.0+dfsg-1 (44 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
freerdp33.15.0+dfsg-2.1 ... 3.28.0+dfsg-2 (37 versions)3.29.0+dfsg-1—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 36× in last 7d / 175× 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 346 total refreshes for this CVE.

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

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-66402?
CVE-2026-66402 is a critical vulnerability published on August 1, 2026. FreeRDP before 3.29.0 (affected versions <= 3.28.0) contains multiple TLS certificate identity validation weaknesses in tlsverifycertificate(), tlsmatchhostname(), and x509utilsgetdnsnames(). Because FreeRDP performs custom Common Name and DNS SAN string matching instead of using OpenSSL's…
When was CVE-2026-66402 disclosed?
CVE-2026-66402 was first published in the National Vulnerability Database on August 1, 2026, with the most recent update on August 31, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-66402 actively exploited?
CVE-2026-66402 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 78.6% of all scored CVEs.
What is the CVSS score of CVE-2026-66402?
CVE-2026-66402 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-66402?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-66402, 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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