CVE-2026-113868
CVE-2026-113868
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.
Vulnerability class: Buffer Overflow
Published .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-113868?
- CVE-2026-113868 is a medium-severity vulnerability, classified under Out-of-bounds Read. CVSS score: 5.3/10. Published 2026-10-20.
- How severe is CVE-2026-113868?
- Medium severity. CVSS v3 base score is 5.3 out of 10.