CVE-2026-126133

UNKNOWN 0.0

Calendar server credentials could be sent to an HTTP proxy

CVSS Score

0.0

EPSS Score

0.0%

EPSS Percentile

0th

When a CalDAV or ICS calendar was accessed through an HTTP proxy that requested authentication, Thunderbird could answer the proxy with the calendar server's username and password. This affected both setting up a new calendar and syncing existing calendars, where a saved password could be sent without any user interaction. A malicious or compromised proxy could use this to obtain the calendar credentials, even for calendars served over HTTPS. This vulnerability was fixed in Thunderbird 160 and Thunderbird 153.7.

Vendor	mozilla
Product	thunderbird
Ecosystems	Browser JavaScript
Industries	Technology
Published	Nov 10, 2026
Last Updated	Nov 10, 2026

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Affected Versions

Mozilla / Thunderbird

All versions affected

References

NVD ↗ CVE.org ↗ EPSS Data ↗

bugzilla.mozilla.org: https://bugzilla.mozilla.org/show_bug.cgi?id=2083485 mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-128/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-129/

Credits

Christopher Bohn (Protectstar Inc.)