Out-of-Bounds Read in FreeRDP MS-RDPECAM Channel

Executive Summary

CVE-2026-57157 is an out-of-bounds heap read vulnerability in FreeRDP server implementations that have the MS-RDPECAM camera device enumerator channel enabled. The vulnerability arises because the server scans attacker-supplied DeviceName and VirtualChannelName fields for a null terminator but then dereferences the pointer one byte beyond the scanned boundary without re-checking if it is still within the valid buffer. If the fields are not properly null-terminated and fill the buffer exactly, this leads to reading memory beyond the allocated heap buffer.

This flaw allows a malicious RDP client to trigger a 1- to 2-byte out-of-bounds read, potentially causing a denial of service by crashing the server process if the read lands on unmapped memory. The issue was fixed in FreeRDP version 3.28.0 by improving the parsing logic to correctly handle null terminators and bounds checking.

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Impact Analysis

This vulnerability can be exploited by a malicious RDP client to cause a denial of service (DoS) on the FreeRDP server by triggering a crash. The out-of-bounds read may cause the server process to access invalid memory, leading to a crash and service interruption.

The CVSS score indicates a medium severity impact with a base score of 6.5, reflecting the potential for confidentiality loss (limited data exposure) and availability impact (server crash). There is no indication that this vulnerability allows code execution or privilege escalation.

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Detection Guidance

This vulnerability involves an out-of-bounds heap read triggered by a malicious RDP client sending specially crafted DeviceName and VirtualChannelName fields without proper null terminators to a FreeRDP server with the MS-RDPECAM channel enabled.

Detection would involve monitoring FreeRDP server logs or network traffic for abnormal or malformed RDP camera device enumerator channel messages, especially those with unusually long or unterminated DeviceName or VirtualChannelName fields.

Since the vulnerability is triggered by malformed RDP messages, you can detect attempts by capturing and analyzing RDP traffic on port 3389 using tools like Wireshark or tcpdump, looking for packets related to the rdpecam channel.

No specific detection commands are provided in the available resources.

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Mitigation Strategies

The primary mitigation step is to upgrade FreeRDP server implementations to version 3.28.0 or later, where the vulnerability has been fixed.

If upgrading immediately is not possible, consider disabling the MS-RDPECAM camera device enumerator channel to prevent processing of the vulnerable code paths.

Additionally, restricting access to the RDP server to trusted clients and enabling authentication before opening dynamic virtual channels can reduce the risk of exploitation.

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Compliance Impact

The provided information does not specify any direct impact of CVE-2026-57157 on compliance with common standards and regulations such as GDPR or HIPAA.

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