Quick answers
- Is CVE-2026-118177 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-118177 being exploited in the wild.
- How severe is CVE-2026-118177?
- Informational severity, published 27 October 2026.
- Which products and versions are affected?
- Mozilla Thunderbird before 159; before 153.6.
- Is there a fix for CVE-2026-118177?
- Yes: fixed in Thunderbird 159, Thunderbird 153.6. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-118177 attacked?
- It is attacked over the network or from the adjacent network, in a web application.
- Am I affected by CVE-2026-118177?
- Check whether you run Mozilla Thunderbird at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: Thunderbird 159, Thunderbird 153.6
Technical details
When Thunderbird performs calendar directory lookups during account setup or network calendar addition, it does not properly validate calendar location URLs, accepting file: and UNC paths in responses. An attacker controlling the calendar server or intercepting unencrypted HTTP traffic can inject malicious calendar locations pointing to local files or remote SMB shares, causing Thunderbird to automatically subscribe to those locations. On Windows, accessing remote UNC paths triggers NTLM credential leaks on each calendar refresh, and attackers can modify calendar files or overwrite local files through the subscription mechanism.
Affected products
- Mozilla Thunderbird before 159; before 153.6
Timeline
- 2026-10-27: disclosed