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

Medium 5.9 Published 14 Feb 2023 Updated 10 Mar 2025

An integer overflow in GSS-NTLMSSP allows out-of-bounds reads leading to denial of service when processing large NTLM tokens.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2023-25563?

CVE-2023-25563 is a medium-severity vulnerability in gssapi gss-ntlmssp, published on 14 Feb 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Weakness: CWE-125

Which versions are affected by CVE-2023-25563?

It affects 1 product.

Products include Gss-Ntlmssp Project Gss-Ntlmssp.

How do I fix CVE-2023-25563?

Upgrade to a fixed version.

Is CVE-2023-25563 being exploited?

There is no known exploitation of CVE-2023-25563 in the wild and no public exploit code.

Sources

Also known as AZL-43480, AZL-44733, DEBIAN-CVE-2023-25563, GHSA-jjjx-5qf7-9mgf, ROOT-OS-UBUNTU-2204-CVE-2023-25563, UBUNTU-CVE-2023-25563.