Acceptance of Extraneous Untrusted Data With Trusted Data Affecting thunderbird package, versions *


Severity

Recommended
0.0
medium
0
10

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
0.19% (9th percentile)

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  • Snyk IDSNYK-RHEL10-THUNDERBIRD-22437942
  • published12 Nov 2026
  • disclosed10 Nov 2026

Introduced: 10 Nov 2026

NewCVE-2026-126135  (opens in a new tab)
CWE-349  (opens in a new tab)

How to fix?

There is no fixed version for RHEL:10 thunderbird.

NVD Description

Note: Versions mentioned in the description apply only to the upstream thunderbird package and not the thunderbird package as distributed by RHEL. See How to fix? for RHEL:10 relevant fixed versions and status.

If an attacker was able to perform a man-in-the-middle attack on an SMTP or POP3 server connection using STARTTLS, the attacker could inject server responses before the TLS handshake completed. Thunderbird would process these responses after the handshake, as if they had been received from the server over the encrypted connection. This could be used to make Thunderbird report a different outcome for sending or fetching mail, and to show attacker-controlled text in error messages. The encrypted connection itself was not compromised, and credentials were not exposed. Connections using SSL/TLS instead of STARTTLS were not affected. This vulnerability was fixed in Thunderbird 160 and Thunderbird 153.7.

CVSS Base Scores

version 3.1