CVE-2026-118177

thunderbird: When looking for calendars in a directory on a server, during account setup or when adding a new network calendar, Th...

CVE-2026-118177 is fixed in thunderbird on 1 platform, first by DEBIAN-CVE-2026-118177, released October 31, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

Urgent
CVSS
9.1
critical
Exploitation
None reported
No vendor assessment
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.0045
39th percentile

When looking for calendars in a directory on a server, during account setup or when adding a new network calendar, Thunderbird accepted calendar locations pointing to other servers, local files or network shares. A malicious server, or a network attacker when the lookup used plain HTTP, could make Thunderbird subscribe to such a location. On Windows this could leak the user's NTLM credentials to an attacker-controlled host on every calendar refresh, and changes to the calendar could be written to the attacker's share or overwrite a local file. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.

Where it's fixed

ProductFixed inFixReleased
Linux
thunderbird · Debian 12.15 (bookworm) 1:153.6.0esr-1~deb12u2 DEBIAN-CVE-2026-118177 Oct 31, 2026
thunderbird · Debian 13.5 (trixie) 1:153.6.0esr-1~deb13u1 DEBIAN-CVE-2026-118177 Oct 31, 2026

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