What’s Vulnerable › Vulnerabilities

CVE-2026-113868: Uninitialized memory disclosure and out-of-bounds read in POP3 and SMTP NTLM authentication

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-20 · updated 2026-10-22
• Weakness: CWE-125

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.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=2076569
• https://www.mozilla.org/security/advisories/mfsa2026-114/
• https://www.mozilla.org/security/advisories/mfsa2026-115/

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