Vulnerability · Published Jun 25, 2025 · Assigned by zdi

CVE-2025-6444ServiceStack GetErrorResponse Improper Input Validation NTLM Relay Vulnerability

Medium 5.9

In plain English

A medium-severity improper input validation in ServiceStack from ServiceStack. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 42% of all known vulnerabilities).

Severity (CVSS 3.0)5.9Medium

Exploit odds (30 days)0.5%top 57.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
ServiceStack	ServiceStack	8.4.0

Weakness: CWE-20 · Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

References

ZDI-25-415 x_research-advisory