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CVE Vulnerability Details :
CVE-2026-66402
PUBLISHED
More InfoOfficial Page
Assigner-VulnCheck
Assigner Org ID-83251b91-4cc7-4094-a5c7-464a1b83ea10
View Known Exploited Vulnerability (KEV) details
Published At-01 Aug, 2026 | 12:22
Updated At-01 Aug, 2026 | 12:22
Rejected At-
▼CVE Numbering Authority (CNA)
FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass

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.

Affected Products
Vendor
FreeRDPFreeRDP
Product
FreeRDP
Default Status
unaffected
Versions
Affected
  • From 0 before 3.29.0 (semver)
Unaffected
  • 3.29.0 (semver)
Problem Types
TypeCWE IDDescription
CWECWE-295Improper Certificate Validation
Type: CWE
CWE ID: CWE-295
Description: Improper Certificate Validation
Metrics
VersionBase scoreBase severityVector
4.09.3CRITICAL
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
3.19.8CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Version: 4.0
Base score: 9.3
Base severity: CRITICAL
Vector:
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Version: 3.1
Base score: 9.8
Base severity: CRITICAL
Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions

Configurations

Workarounds

Exploits

Credits

reporter
1121984919
Timeline
EventDate
Replaced By

Rejected Reason

References
HyperlinkResource
https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-43hh-p3vw-hfx3
vendor-advisory
https://github.com/FreeRDP/FreeRDP/commit/b9533f07f98c25ed01c5f543b4d0ce73e120f5fd
patch
https://www.vulncheck.com/advisories/freerdp-before-tls-certificate-identity-validation-bypass
third-party-advisory
Hyperlink: https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-43hh-p3vw-hfx3
Resource:
vendor-advisory
Hyperlink: https://github.com/FreeRDP/FreeRDP/commit/b9533f07f98c25ed01c5f543b4d0ce73e120f5fd
Resource:
patch
Hyperlink: https://www.vulncheck.com/advisories/freerdp-before-tls-certificate-identity-validation-bypass
Resource:
third-party-advisory
Details not found