Sources: National Vulnerability Database, CVE.org, CISA KEV, FIRST EPSS
CVE-2026-121392 Overview
FreeRDP before 3.32.2 contains an improper certificate validation vulnerability in tls_verify_certificate() that accepts Common Name fallback despite non-matching SAN entries and matches IP literals against DNS strings. Man-in-the-middle attackers holding a certificate from a client-trusted CA can bypass server identity checks to intercept RDP sessions, including keystrokes, clipboard, and screen content.
Critical Impact
Affected Products
- FreeRDP: see the vendor advisory for the exact affected versions
Discovery Timeline
- 2026-11-03: CVE-2026-121392 published to the National Vulnerability Database by disclosure@vulncheck.com
- 2026-11-03: last updated in the NVD database
Technical Details for CVE-2026-121392
Vulnerability Analysis
CVE-2026-121392 is a Security Vulnerability weakness (CWE-295) in FreeRDP. Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction.
With a CVSS base score of 9.1, apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Root Cause
The vendor description states: FreeRDP before 3.32.2 contains an improper certificate validation vulnerability in tls_verify_certificate() that accepts Common Name fallback despite non-matching SAN entries and matches IP literals against DNS strings. Man-in-the-middle attackers holding a certificate from a client-trusted CA can bypass server identity checks to intercept RDP sessions, including keystrokes, clipboard, and screen content.
Attack Vector
Based on the CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. Attack complexity is high complexity.
No exploitation in the wild is confirmed by CISA at the time of the last update. Check the references below for any vendor or researcher proof of concept.
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Detection Methods for CVE-2026-121392
Detection Strategies
- Inventory every instance of FreeRDP and compare the running version with the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Run an authenticated vulnerability scan once your scanner ships a check for this CVE.
Monitoring Recommendations
- Forward FreeRDP application, access and audit logs to your SIEM for retrospective hunting.
- Alert on new processes, configuration changes or outbound connections from the affected service.
- Track the vendor advisory and the CISA KEV catalog for changes in exploitation status.
How to Mitigate CVE-2026-121392
Immediate Actions Required
- Apply the fixed version of FreeRDP named in the vendor advisory.
- Prioritize internet facing and business critical instances first.
- Rescan after the change to confirm the exposure is closed.
Patch Information
Use the fixed version listed in the vendor advisory for FreeRDP.
Workarounds
- If patching must wait, restrict network access to the affected service and place it behind authentication or a web application firewall rule.
CWE References
Technical References
This entry is built directly from NVD, CISA KEV and EPSS data. Verify fixed versions in the vendor advisory before you deploy.
Frequently asked questions
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