CVE-2026-91960
Received Received - Intake

Integer Overflow in FreeRDP Leading to Denial of Service

Publication date: 2026-09-15

Last updated on: 2026-09-15

Assigner: VulnCheck

Description
FreeRDP versions before 3.31.0 contain an integer overflow in WinPR's Stream_EnsureRemainingCapacity function that allows remote attackers to cause denial of service. A malicious RD Gateway peer can send a WebSocket Ping frame with a crafted 64-bit extended payload length to trigger integer wraparound, resulting in a double free that crashes the FreeRDP client during connection.

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Meta Information

Published
2026-09-15
Last Modified
2026-09-15
Generated
2026-09-15
AI Q&A
2026-09-15
EPSS Evaluated
N/A
NVD
CVE-2026-91960
EUVD
EUVD-2026-78636

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
freerdp freerdp to 3.31.0 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-190 The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

Attack-Flow Graph

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Executive Summary

CVE-2026-91960 is an integer overflow vulnerability in FreeRDP versions before 3.31.0. It occurs in the WinPR library's Stream_EnsureRemainingCapacity function. A remote attacker can exploit this by sending a malicious WebSocket Ping frame with a crafted 64-bit payload length. This triggers an integer wraparound, leading to a double free error that crashes the FreeRDP client during connection.

Detection Guidance

To detect this vulnerability, check the FreeRDP version on your system using commands like 'xfreerdp --version' or 'apt list --installed | grep freerdp'. If the version is below 3.31.0, the system is vulnerable. Monitor network traffic for WebSocket Ping frames with crafted payload lengths, particularly from RD Gateway peers.

Impact Analysis

This vulnerability allows a remote attacker to cause a denial of service by crashing the FreeRDP client. The exploit can be triggered before authentication via a hostile RD Gateway, preventing normal RDP connections. The impact may vary depending on the C library used, with some systems detecting the double-free and aborting while others may experience memory corruption.

Compliance Impact

This vulnerability primarily causes denial of service by crashing FreeRDP clients, which could disrupt services handling sensitive data. While not directly violating GDPR or HIPAA, such disruptions may impact availability requirements for systems processing personal or health data. Organizations must ensure patches are applied to maintain compliance with availability obligations under these regulations.

Mitigation Strategies

Immediately upgrade FreeRDP to version 3.31.0 or later. If upgrading is not possible, restrict network access to RD Gateway peers or disable WebSocket Ping frames if not required. Apply network-level mitigations to filter malicious payloads.

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