Executive brief
A security flaw exists in the .NET component used for handling TAR archive files. An attacker could use a specially crafted archive to write files to unauthorized locations on a computer, potentially overwriting critical system or application files. This could lead to system instability or unauthorized changes to software configuration.
Technical details
A tampering vulnerability (CWE-59) exists in the System.Formats.Tar library within the TarFile.ExtractToDirectory method. The root cause is improper link resolution (symlink path traversal) during the extraction process. A local attacker can provide a malicious TAR archive containing symbolic links that, when extracted, allow the attacker to perform arbitrary file writes outside of the target extraction directory. This can result in the modification of sensitive files or application binaries. Microsoft has released patches for .NET 8, 9, and 10 to address this issue.
Affected products
- Microsoft Microsoft.NETCore.App.Runtime >= 8.0.0, <= 8.0.27; >= 9.0.0, <= 9.0.16; >= 10.0.0, <= 10.0.8
Timeline
- 2026-06-09: disclosed: Initial advisory publication
- 2026-06-09: patched: Patched versions 8.0.28, 9.0.17, and 10.0.9 released
- 2026-06-16: advisory: GitHub Advisory reviewed and updated