FreeRDP <3.21.0 ClearCodec OOB Read/Write Leading to Heap Buffer Overflow
CVE-2026-23531 Published on January 19, 2026
FreeRDP has heap-buffer-overflow in clear_decompress
FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to version 3.21.0, in ClearCodec, when `glyphData` is present, `clear_decompress` calls `freerdp_image_copy_no_overlap` without validating the destination rectangle, allowing an out-of-bounds read/write via crafted RDPGFX surface updates. A malicious server can trigger a clientside heap buffer overflow, causing a crash (DoS) and potential heap corruption with codeexecution risk depending on allocator behavior and surrounding heap layout. Version 3.21.0 contains a patch for the issue.
Weakness Type
Heap-based Buffer Overflow
A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
Products Associated with CVE-2026-23531
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Affected Versions
FreeRDP Version < 3.21.0 is affected by CVE-2026-23531Exploit 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.