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VulnerabilityPublished

CVE-2026-126133: Mozilla Thunderbird · Calendar server credentials could be sent to an HTTP proxy

Affects Mozilla ThunderbirdSource CVE Database V5

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Not known to be exploited.

Data as of 10 Nov 2026, 19:20 UTC

Severity
Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

Thin evidence

One scorer or none

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 10 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

What to do

AI-suggested

This vulnerability has been fixed in Thunderbird version 160. Users and administrators should upgrade to Thunderbird 160 or later to remediate this issue. No additional mitigation steps are required once the update is applied.

Description

CVE-2026-126133 is a vulnerability in Mozilla Thunderbird where calendar server credentials could be inadvertently sent to an HTTP proxy requiring authentication. This occurs when accessing CalDAV or ICS calendars through such a proxy, allowing the proxy to receive the calendar server's username and password without user interaction. The issue affects both new calendar setups and syncing existing calendars, and can expose credentials even if the calendar server uses HTTPS. The vulnerability was fixed in Thunderbird version 160.

References

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