CVE-2026-91949
Received Received - Intake

FreeRDP Server Protocol Negotiation Bypass Vulnerability

Publication date: 2026-09-15

Last updated on: 2026-09-15

Assigner: VulnCheck

Description
FreeRDP server versions before 3.31.0 contain a protocol negotiation bypass vulnerability that allows unauthenticated attackers to establish RDSTLS connections despite server policy disabling them. Attackers can send incompatible protocol requests, receive negotiation failures, then complete TLS handshake and enter RDSTLS to bypass pre-authentication transport restrictions.

CVSS Scores

EPSS Scores

Probability:
Percentile:

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-2026-91949
EUVD
EUVD-2026-78806

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
freerdp freerdp From 3.0.0 (inc) to 3.31.0 (exc)
freerdp freerdp to 3.31.0 (exc)

Helpful Resources

Exploitability

CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-693 The product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product.

Attack-Flow Graph

AI Quick Actions

Instant insights powered by AI
Executive Summary

FreeRDP server versions before 3.31.0 have a protocol negotiation bypass flaw. Unauthenticated attackers can send incompatible protocol requests, receive negotiation failures, then complete a TLS handshake to enter RDSTLS mode. This bypasses server policy restrictions that disable RDSTLS connections before authentication.

Impact Analysis

Attackers could exploit this to bypass pre-authentication transport restrictions, potentially gaining unauthorized access to the FreeRDP server. This may lead to remote code execution, data theft, or further network compromise depending on server configuration and exposed services.

Compliance Impact

This vulnerability could violate compliance requirements that mandate secure authentication and transport protocols, such as GDPR's data protection measures or HIPAA's access controls. Unauthorized access risks may lead to data breaches, triggering regulatory penalties and reputational damage.

Mitigation Strategies

Upgrade FreeRDP server to version 3.31.0 or later to address the protocol negotiation bypass vulnerability. Ensure server policies are correctly configured to enforce RDSTLS restrictions.

Chat Assistant

Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-91949. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70

EPSS Chart