CVE-2026-66402

CRITICALPre-NVD 9.89.8—
EchelonGraph scoreHIGH 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(high)
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
22%
KEV
Not listed

Published

August 1, 2026

Last Modified

August 5, 2026

Advisory Details (3)

Auto-updated Aug 19, 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 ... 3.30.0+dfsg-1~bpo13+1 (43 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 57× in last 7d / 169× 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 169 total refreshes for this CVE.

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

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 5, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-66402 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 78.3% 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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