Quick answers
- Is CVE-2026-126134 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-126134 being exploited in the wild.
- How severe is CVE-2026-126134?
- Informational severity, published 10 November 2026.
- Which products and versions are affected?
- Mozilla Thunderbird before 160.
- Is there a fix for CVE-2026-126134?
- Yes: fixed in Thunderbird 160. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-126134 attacked?
- It is attacked over the network, in a web application.
- Am I affected by CVE-2026-126134?
- 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 160
Technical details
Thunderbird did not properly validate file: URLs in feed subscriptions, allowing subscription to URLs that point to network shares. When the feed was fetched, Windows automatically included NTLM authentication credentials in the request to the attacker's server. The vulnerability requires user interaction (subscribing to a malicious feed) and only affects Windows systems; the fix was released in Thunderbird 160.
Affected products
- Mozilla Thunderbird before 160
Timeline
- 2026-11-10: disclosed
- 2026-11-10: patched: fixed in Thunderbird 160