CVE-2026-126133: Mozilla Thunderbird · Calendar server credentials could be sent to an HTTP proxy
Affects Mozilla ThunderbirdSource CVE Database V5
Not known to be exploited.
Data as of 10 Nov 2026, 19:20 UTC
Rated by Threat Radar · CVSS not yet scored by NVD
Thin evidence
One scorer or noneExploitation evidence
Disclosed: evidence found.
CVE published 10 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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.