FreeRDP 3.20.1: fixed global-buffer-overflow in Base64 decoder (Arm/AArch64)
CVE-2026-22858 Published on January 14, 2026
FreeRDP has a global-buffer-overflow in crypto_base64_decode
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.
Weakness Types
Out-of-bounds Read
The software reads data past the end, or before the beginning, of the intended buffer. Typically, this can allow attackers to read sensitive information from other memory locations or cause a crash. A crash can occur when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string. The expected sentinel might not be located in the out-of-bounds memory, causing excessive data to be read, leading to a segmentation fault or a buffer overflow. The software may modify an index or perform pointer arithmetic that references a memory location that is outside of the boundaries of the buffer. A subsequent read operation then produces undefined or unexpected results.
Reliance on Undefined, Unspecified, or Implementation-Defined Behavior
The software uses an API function, data structure, or other entity in a way that relies on properties that are not always guaranteed to hold for that entity. This can lead to resultant weaknesses when the required properties change, such as when the software is ported to a different platform or if an interaction error (CWE-435) occurs.
Products Associated with CVE-2026-22858
Want to know whenever a new CVE is published for FreeRDP? stack.watch will email you.
Affected Versions
FreeRDP Version < 3.20.1 is affected by CVE-2026-22858Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.