CVE-2026-40254: FreeRDP: contains_dotdot() off-by-one allows drive channel path traversal via terminal ..

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-04-24 · updated 2026-06-17
Weakness: CWE-193

Description

FreeRDP is a free implementation of the Remote Desktop Protocol. Versions prior to 3.25.0 have an off-by-one in the path traversal filter in `channels/drive/client/drive_file.c`. The `contains_dotdot()` function catches `../` and `..\` mid-path but misses `..` when it's the last component with no trailing separator. A rogue RDP server can read, list, or write files one directory above the client's shared folder through RDPDR requests. This requires the victim to connect with drive redirection enabled. Version 3.25.0 patches the issue.

Affected products

FreeRDP: before 3.25.0 — fixed in 3.25.0

How to fix

Upgrade to a fixed version: FreeRDP 3.25.0. Check the vendor advisory for mitigations.

References

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