Microsoft Windows TAR File Parsing NTLM Relay Vulnerability

October 14th, 2025
ZDI-25-953 ZDI-CAN-27289

CVE ID

CVE-2025-59284

CVSS Score

3.3 AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

Affected Vendors

Microsoft

Affected Products

Windows

Vulnerability Details

This vulnerability allows remote attackers to relay NTLM credentials on affected installations of Microsoft Windows. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.

The specific flaw exists within the parsing of TAR files. A crafted hard link in a TAR file can trigger an outgoing SMB request. An attacker can leverage this vulnerability to relay NTLM credentials in the context of the current user.

Additional Details

Microsoft has issued an update to correct this vulnerability. More details can be found at:
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-59284

Disclosure Timeline

  • 2025-07-25 - Vulnerability reported to vendor
  • 2025-10-14 - Coordinated public release of advisory
  • 2025-10-14 - Advisory Updated

Credit

Len Sadowski and Oguz Bektas

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