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: 0.5%CVSS: 9.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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
9.8CRITICALmedium confidence
EG Risk
59
EG Risk 59/100CISA SSVC

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%
Exploitation1% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
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
41st
KEV
Not listed

CISA SSVCTrack 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 none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 1, 2026

Last Modified

October 2, 2026

Advisory Details (3)

Auto-updated Oct 2, 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 rangeFix by version rangeDependents
freerdp22.10.0+dfsg1-1 ... 2.9.0+dfsg1-1~bpo11+1 (32 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
freerdp22.10.0+dfsg1-1 ... 2.11.7+dfsg1-6~deb12u1 (13 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
freerdp33.15.0+dfsg-2.1 ... 3.32.1+dfsg-1~bpo13+1 (49 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
freerdp33.15.0+dfsg-2.1 ... 3.28.0+dfsg-2 (37 versions)
  • every version up to 3.29.0+dfsg-1: fixed in 3.29.0+dfsg-1
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 24× in last 7d / 137× 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 398 total refreshes for this CVE.

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

Related CVEs(same product + 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 on August 1, 2026, with the most recent update on October 2, 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 0.5% probability of exploitation in the next 30 days (41st percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-66402?
CVE-2026-66402 has a CVSS base score of 9.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-66402?
A fix for CVE-2026-66402 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-66402 are linked in the Vendor Advisories panel on this page.

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