CVE-2026-113868 Uninitialized memory disclosure and out-of-bounds read in POP3 and SMTP NTLM authentication
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-113868?
CVE-2026-113868 is a medium-severity vulnerability in Mozilla Thunderbird, published on 20 Oct 2026.
Official description
When authenticating to a POP3 or SMTP server using NTLM, Thunderbird did not check whether the server's challenge was valid base64. A malicious server could send a challenge that caused Thunderbird to include uninitialized heap memory in its NTLM response, disclosing that memory to the server. A challenge consisting only of base64 padding also caused an out-of-bounds read, crashing Thunderbird. This affected accounts configured to use NTLM or GSSAPI authentication. The uninitialized memory disclosure only affected NTLM. This vulnerability was fixed in Thunderbird 158.0.1 and Thunderbird 153.5.1.
Weakness: CWE-125
Which versions are affected by CVE-2026-113868?
How do I fix CVE-2026-113868?
Upgrade to a fixed version.
Is CVE-2026-113868 being exploited?
There is no known exploitation of CVE-2026-113868 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-113868, GHSA-v77j-vmg8-85hq, UBUNTU-CVE-2026-113868.