Improper input validation in Servicestack

CVE-2025-6444

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.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

EPSS: 0.004 (32.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N.

Affected products

Weakness classification (CWE)

Public proof-of-concept exploits

References

Frequently asked questions

What is CVE-2025-6444?
CVE-2025-6444 is a medium-severity vulnerability in Servicestack, classified under Improper Input Validation. CVSS score: 5.9/10. Published 2025-06-25.
How severe is CVE-2025-6444?
Medium severity. CVSS v3 base score is 5.9 out of 10.
Is CVE-2025-6444 known to be exploited?
1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.