AIKIDO-2026-432105
FreeRDP.FreeRDP is vulnerable to Improper Certificate Validation
31
Low Risk
This Affects:
FreeRDP.FreeRDPTL;DR
FreeRDP performs custom Common Name and DNS subjectAltName string matching in its TLS certificate verification instead of using length-aware identity validation. Embedded NUL bytes in a DNS SAN are truncated, a matching Common Name is accepted even when non-matching DNS SAN entries are present, and IP-literal targets are matched against DNS SAN values without checking the iPAddress SAN. A certificate that a strict verifier would reject can therefore be accepted for a different identity. The fix delegates DNS and IP identity checks to length-aware validation and rejects malformed SAN data.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and you rely on FreeRDP TLS certificate hostname or IP identity validation rather than auto-accepting certificates.
Background info
FreeRDP.FreeRDP is vulnerable to Improper Certificate Validation in versions 0.0.1 - 3.28.0.
How to fix this
Upgrade the FreeRDP.FreeRDP library to the patch version.
Links
GitHub Release
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