ServiceStack GetErrorResponse Improper Input Validation NTLM Relay Vulnerability

Description

ServiceStack GetErrorResponse Improper Input Validation NTLM Relay Vulnerability. This vulnerability allows remote attackers to relay NTLM credentials on affected installations of ServiceStack. Interaction with this library is required to exploit this vulnerability but attack vectors may vary depending on the implementation. The specific flaw exists within the implementation of the GetErrorResponse method. The issue results from the lack of proper validation of user-supplied data, which can result in a type confusion condition. An attacker can leverage this vulnerability to relay NTLM credentials in the context of the current user. Was ZDI-CAN-25834.

Scores

EPSS (exploitation in 30 days)

0.49% · top 58% of all CVEs (5 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.9.

Weakness

• CWE-20: Improper Input Validation (opens in a new tab)All about CWE-20 and its CVEs

Affected products

• ServiceStack · ServiceStack

  • affected 8.4.0

References (1)

• ZDI-25-415 (opens in a new tab)x_research-advisory

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2025-6444](https://trackcve.app/badge/CVE-2025-6444.svg)](https://trackcve.app/cve/CVE-2025-6444)

Record last updated 25 Jun 2025, 18:09 UTC.