CVE-2026-22858
CriticalCVSS 9.1Exploitation Probability (EPSS)
Low risk45th percentile - higher than 45% of all known CVEs
Summary
In FreeRDP before version 3.20.1, a global buffer overflow was observed in the Base64 decoding path. The root cause is implementation-defined char signedness: on Arm/AArch64 builds, plain char is treated as unsigned, so the guard c <= 0 can be optimized into a simple c != 0 check, allowing non-ASCII bytes (0x80-0xFF) to bypass the intended range restriction and be used as an index into a global lookup table, causing out-of-bounds access.
Risk Assessment
An attacker can remotely crash the RDP server or potentially access out-of-bounds memory, leading to data leakage or further privilege escalation.
Recommendation
Immediately update FreeRDP to version 3.20.1 or later, which contains the fix for this vulnerability.
Original NVD description (English source)
FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.20.1, global-buffer-overflow was observed in FreeRDP's Base64 decoding path. The root cause appears to be implementation-defined char signedness: on Arm/AArch64 builds, plain char is treated as unsigned, so the guard c <= 0 can be optimized into a simple c != 0 check. As a result, non-ASCII bytes (e.g., 0x80-0xFF) may bypass the intended range restriction and be used as an index into a global lookup table, causing out-of-bounds access. This vulnerability is fixed in 3.20.1.