CVE-2026-91948
Received Received - Intake

Out-of-Bounds Write in FreeRDP Server Static Virtual Channel

Publication date: 2026-09-15

Last updated on: 2026-09-15

Assigner: VulnCheck

Description
FreeRDP versions before 3.31.0 contain an out-of-bounds write vulnerability in server-side static virtual channel handling when CHANNEL_OPTION_SHOW_PROTOCOL is enabled. Authenticated clients can queue oversized channel messages that cause buffer underflow and corrupt heap memory including live pointers, potentially enabling code execution.

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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-2026-91948
EUVD
EUVD-2026-78805

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-191 The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

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Executive Summary

FreeRDP versions before 3.31.0 have an out-of-bounds write flaw in server-side static virtual channel handling when CHANNEL_OPTION_SHOW_PROTOCOL is enabled. Authenticated clients can send oversized channel messages that cause buffer underflow, corrupting heap memory including live pointers, which may lead to code execution.

Detection Guidance

Detecting this vulnerability requires checking FreeRDP versions and monitoring for suspicious channel message handling. Use commands like 'xfreerdp --version' or 'apt list --installed | grep freerdp' to verify installed versions. Inspect logs for heap corruption errors or unexpected channel message sizes during RDP sessions.

Impact Analysis

An attacker with authenticated access could exploit this to corrupt memory, potentially executing arbitrary code on the FreeRDP server. This may lead to unauthorized system access, data breaches, or service disruption depending on the server's role.

Compliance Impact

This vulnerability could lead to unauthorized access or data breaches, violating confidentiality requirements in GDPR and HIPAA. Organizations using vulnerable FreeRDP versions may face compliance violations, legal penalties, and reputational damage.

Mitigation Strategies

Upgrade FreeRDP to version 3.31.0 or later immediately. Disable CHANNEL_OPTION_SHOW_PROTOCOL if not required. Restrict RDP access to trusted networks and users. Monitor for unusual activity or crashes in RDP sessions.

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