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OpenAdvisories
Critical · 9.8 CVE-2026-66402 EUVD-2026-51851GHSA-759r-h698-g7xj

FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass

Published Aug 1, 2026 · Updated Aug 5, 2026 · Assigned by VulnCheck

Description

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

VendorProductAffectedFixed
FreeRDP FreeRDP < 3.29.0 3.29.0

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
Debian 14 freerdp3 3.29.0+dfsg-1 —
Debian 13 freerdp3 No fix yet —
Debian 12 freerdp2 No fix yet —
ReleasePackageFixed inAdvisory
Ubuntu 26.04 LTS freerdp3 3.30.0+dfsg-0ubuntu0.26.04.1 —
Ubuntu 24.04 LTS freerdp3 3.30.0+dfsg-0ubuntu0.24.04.1 —
Ubuntu 22.04 LTS freerdp2 No fix yet —
Ubuntu 18.04 LTS freerdp No fix yet —
Ubuntu 16.04 LTS freerdp No fix yet —
Show 3 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Ubuntu Pro 24.04 LTS freerdp2 No fix yet —
Ubuntu Pro 20.04 LTS freerdp2 No fix yet —
Ubuntu Pro 18.04 LTS freerdp2 No fix yet —

Amazon Linux

ReleasePackageFixed inAdvisory
Amazon Linux 2023 freerdp +5 2:3.6.3-1.amzn2023.0.15 ALAS2023-2026-2111
Amazon Linux 2 freerdp +4 2:2.11.7-1.amzn2.0.14 ALAS2-2026-3887

Advisories 3

References