CVE-2024-32040 in FreeRDP
Summary
by MITRE • 04/23/2024
FreeRDP is a free implementation of the Remote Desktop Protocol. FreeRDP based clients that use a version of FreeRDP prior to 3.5.0 or 2.11.6 and have connections to servers using the `NSC` codec are vulnerable to integer underflow. Versions 3.5.0 and 2.11.6 patch the issue. As a workaround, do not use the NSC codec (e.g. use `-nsc`).
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Analysis
by VulDB Data Team • 11/20/2024
The vulnerability identified as CVE-2024-32040 affects FreeRDP implementations that process Remote Desktop Protocol connections using the NSC codec, presenting a critical integer underflow condition that could enable remote code execution or denial of service attacks. This flaw exists in FreeRDP versions prior to 3.5.0 and 2.11.6, where the protocol handling logic fails to properly validate input parameters during NSC codec processing. The issue stems from insufficient boundary checking when calculating buffer sizes or frame dimensions, leading to scenarios where arithmetic operations produce values that fall below the minimum representable integer, creating exploitable conditions in memory management.
The technical implementation of this vulnerability occurs within the NSC codec processing module where unsigned integer arithmetic operations are performed without proper overflow or underflow validation. When a malicious remote server sends specially crafted NSC-encoded data, the client application processes these values through mathematical operations that result in integer underflow conditions. This behavior manifests as memory corruption that can be exploited to overwrite adjacent memory regions, potentially allowing attackers to execute arbitrary code or cause application crashes. The vulnerability aligns with CWE-191, which specifically addresses integer underflow conditions, and represents a classic example of improper input validation in network protocol implementations.
From an operational perspective, this vulnerability poses significant risk to organizations relying on FreeRDP-based remote desktop solutions, particularly in environments where untrusted servers might be accessed or where network segmentation is insufficient. The attack vector requires a remote server capable of communicating with the vulnerable client, making it particularly dangerous in scenarios where users connect to external or untrusted remote desktop services. The impact extends beyond simple denial of service to potentially enabling full system compromise, as integer underflow conditions can lead to stack corruption, heap corruption, or other memory-related vulnerabilities that attackers can leverage for privilege escalation. This vulnerability affects the core Remote Desktop Protocol functionality and could impact enterprise environments using FreeRDP for remote access, virtual desktop infrastructure, or remote administration tasks.
The recommended mitigations include immediate upgrade to FreeRDP versions 3.5.0 or 2.11.6, which contain the necessary patches to address the integer underflow condition. Organizations should also implement the workaround of disabling NSC codec usage through command-line parameters such as `-nsc` to prevent exploitation while maintaining operational security. Network segmentation and access controls should be reinforced to limit exposure to untrusted remote servers, and monitoring should be implemented to detect unusual connection patterns or attempts to utilize vulnerable codecs. Security teams should also consider implementing runtime protections such as address space layout randomization and stack canaries to mitigate potential exploitation attempts, though these measures are secondary to the primary patching requirement. The vulnerability demonstrates the importance of proper integer validation in protocol implementations and aligns with ATT&CK technique T1210, which covers exploitation of remote services through protocol manipulation.