CVE-2023-25563: GSS-NTLMSSP vulnerable to multiple out-of-bounds reads when decoding NTLM fields

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-02-14 · updated 2026-06-17
Weakness: CWE-125

Description

GSS-NTLMSSP is a mechglue plugin for the GSSAPI library that implements NTLM authentication. Prior to version 1.2.0, multiple out-of-bounds reads when decoding NTLM fields can trigger a denial of service. A 32-bit integer overflow condition can lead to incorrect checks of consistency of length of internal buffers. Although most applications will error out before accepting a singe input buffer of 4GB in length this could theoretically happen. This vulnerability can be triggered via the main `gss_accept_sec_context` entry point if the application allows tokens greater than 4GB in length. This can lead to a large, up to 65KB, out-of-bounds read which could cause a denial-of-service if it reads from unmapped memory. Version 1.2.0 contains a patch for the out-of-bounds reads.

Affected products

gssapi gss-ntlmssp: before 1.2.0 — fixed in 1.2.0

How to fix

Upgrade to a fixed version: gssapi gss-ntlmssp 1.2.0. Check the vendor advisory for mitigations.

References

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