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Uninitialized memory disclosure and out-of-bounds read in POP3 and SMTP NTLM authentication

Microsoft Windows · CVE-2026-113868
0 news outlets2 CERTs and agencies0 researchers

What is it?

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.

Evidence

CERTs and agencies (2)

Exploitation

  • Public proof of concept
  • Exploited in the wild
  • Listed as known exploited
CVSS
5.3
EPSS
0.4%
First seen
2 d ago
Status
confirmed

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