CVE-2026-126134 Feed subscriptions could leak NTLM credentials on Windows
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Check this codebase for CVE-2026-126134 and fix it if it is affected.
What it is: CVE-2026-126134 is a vulnerability in Mozilla Thunderbird, published on 10 Nov 2026.
Exploitation: There is no known exploitation of CVE-2026-126134 in the wild and no public exploit code.
Affected product: Mozilla Thunderbird. No package-level version data is available, so check the vendor advisory linked from the reference page.
Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.
Reference: https://insights.sbomify.com/CVE-2026-126134/ (Markdown: https://insights.sbomify.com/CVE-2026-126134/index.md)
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-126134?
CVE-2026-126134 is a vulnerability in Mozilla Thunderbird, published on 10 Nov 2026.
Official description
Thunderbird allowed feed subscriptions to file: URLs that point to a network share. If a user was tricked into subscribing to such a URL, Thunderbird connected to the attacker's server when fetching the feed. Windows then sent the user's NTLM credentials to that server. This bug only affects Thunderbird on Windows. Other operating systems are unaffected. This vulnerability was fixed in Thunderbird 160 and Thunderbird 153.7.
Which versions are affected by CVE-2026-126134?
How do I fix CVE-2026-126134?
Upgrade to a fixed version.
Is CVE-2026-126134 being exploited?
There is no known exploitation of CVE-2026-126134 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-126134, GHSA-8cqj-cwhc-fvxg, UBUNTU-CVE-2026-126134.