CVE-2026-96231: CWE-59: Improper Link Resolution Before File Access ('Link Following') in Microsoft .NET 10.0

This vulnerability (CWE-59) in Microsoft.NETCore.App.Runtime affects Unix named-mutex and shared-memory paths on Linux and macOS. Due to insecure global directories, symlink race conditions, and unsafe permission changes, local attackers can exploit improper link resolution before file access to truncate or overwrite files, escalate privileges, or widen directory permissions. The issue impacts multiple runtime package versions from 8.0.0 through 10.0.12 and some preview versions. Microsoft has released official fixes in versions 8.0.32, 9.0.21, 10.0.13, and 11.0.0-rc.2 to remediate the vulnerability.

The vulnerability allows local attackers to manipulate file system objects via symlink races and insecure directory permissions, potentially leading to file truncation or overwriting, permission escalation, and privilege elevation. The CVSS v3.1 score is 7.8 (High), indicating significant confidentiality, integrity, and availability impact on affected systems running vulnerable .NET runtime versions on Linux and macOS.

An official fix is available from Microsoft. Users and developers should update affected Microsoft.NETCore.App.Runtime packages to the patched versions: 8.0.32, 9.0.21, 10.0.13, or 11.0.0-rc.2 as appropriate. Applying these updates will remediate the vulnerability. No additional mitigation steps are indicated by the vendor advisory.