CVE-2026-109249 in FreeRDP
Summary
by MITRE • 10/12/2026
FreeRDP 3.0.0 before 3.32.0 contains a heap out-of-bounds read in freerdp_assistance_parse_all_elements_of() because it advances its parsing cursor without reducing the remaining length, letting the scan window exceed the decrypted ConnectionString2 buffer. Attackers can supply a crafted .msrcIncident invitation file and password that crash xfreerdp when opened, before any RDP connection.
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Analysis
by VulDB Data Team • 10/12/2026
The vulnerability identified in FreeRDP versions prior to 3.32.0 represents a critical heap-based out-of-bounds read condition located within the assistance parsing logic of the client application. Specifically, the flaw resides in the freerdp_assistance_parse_all_elements_of function, which is responsible for processing Microsoft Remote Assistance invitation files and associated password data. This component handles the decryption and subsequent parsing of ConnectionString2 buffers, a standard format used to transmit remote support session details securely. The root cause of this vulnerability stems from an improper management of buffer boundaries during the iterative scanning process. As the parser advances its internal cursor through the decrypted data structure, it fails to decrement or correctly track the remaining length of the available buffer space. This logical error results in a scenario where the scan window is permitted to extend beyond the actual allocated memory region defined by the ConnectionString2 buffer size.
From a technical perspective, this implementation defect allows an attacker who supplies a maliciously crafted .msrcIncident file along with specific password parameters to trigger a heap out-of-bounds read when the victim opens or processes the invitation within xfreerdp. Because this processing occurs before any actual Remote Desktop Protocol connection is established, the attack vector does not require network-level access to an RDP server but rather relies on social engineering or malicious file delivery mechanisms that trick users into opening these specific invitation files. The immediate operational impact of exploiting this flaw is typically a denial of service condition manifested as a crash in the xfreerdp application. While out-of-bounds reads are primarily associated with information disclosure, depending on the memory layout and compiler optimizations, such conditions can potentially lead to further exploitation vectors if sensitive data residing adjacent to the buffer is leaked or if undefined behavior triggers additional instability within the process memory space.
This vulnerability aligns closely with Common Weakness Enumeration category CWE-125, which describes Out-of-bounds Read vulnerabilities where software reads past the end of a buffer. In terms of adversarial tactics and techniques, this flaw can be leveraged to support initial access or execution phases by exploiting user interaction through malicious files, mapping conceptually toward ATT&CK technique T1204, specifically User Execution via Malicious File. The lack of proper bounds checking during the parsing phase highlights a deficiency in input validation practices within the assistance module, which is critical for maintaining the integrity and availability of remote support workflows that rely on FreeRDP as an open-source implementation.
To mitigate this risk, organizations deploying FreeRDP must ensure that all client installations are updated to version 3.32.0 or later, where the parsing logic has been corrected to properly manage buffer lengths during cursor advancement. Security administrators should also implement strict file intake policies for remote assistance invitations, validating their source and integrity before processing. Additionally, enabling sandboxing for applications handling untrusted input can limit the potential impact of such memory corruption vulnerabilities by isolating the process from critical system resources. Regular patch management cycles are essential to address these types of logic errors in widely used open-source infrastructure components that facilitate remote connectivity and support operations.