CVE-2026-20931
Published: 13 January 2026
Summary
CVE-2026-20931 is a high-severity External Control of File Name or Path (CWE-73) vulnerability in Microsoft Windows Server 2008. Its CVSS base score is 8.0 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 26.0% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Directly mitigates CWE-73 external control of file name or path by requiring validation of inputs to the Windows Telephony Service.
Ensures timely remediation of the specific vulnerability in Windows Telephony Service through application of Microsoft's patches.
Limits the impact of privilege escalation by enforcing least privilege on low-privileged processes exploitable over adjacent networks.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
CWE-73 path control in Telephony Service directly enables local privilege escalation to SYSTEM-level access.
NVD Description
External control of file name or path in Windows Telephony Service allows an authorized attacker to elevate privileges over an adjacent network.
Deeper analysisAI
CVE-2026-20931 is a vulnerability classified under CWE-73 (External Control of File Name or Path) in the Windows Telephony Service. Published on 2026-01-13T18:16:20.003, it carries a CVSS v3.1 base score of 8.0 (AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H). The flaw affects Windows systems that utilize the Telephony Service component.
An attacker with low privileges (PR:L) on an adjacent network (AV:A) can exploit this vulnerability with low complexity and no user interaction required. Successful exploitation allows privilege escalation, resulting in high impacts to confidentiality, integrity, and availability.
Microsoft's update guide at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20931 provides details on associated advisories and patches for mitigation.
Details
- CWE(s)