CVE-2026-113866 Account password sent unencrypted during Exchange account setup
Medium 5.9
Published
Updated
Check this codebase for CVE-2026-113866 and fix it if it is affected.
What it is: CVE-2026-113866 is a medium-severity vulnerability in Mozilla Thunderbird, published on 20 Oct 2026.
Exploitation: There is no known exploitation of CVE-2026-113866 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-2026-113866/ (Markdown: https://insights.sbomify.com/CVE-2026-113866/index.md)
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-113866?
CVE-2026-113866 is a medium-severity vulnerability in Mozilla Thunderbird, published on 20 Oct 2026.
Official description
When setting up an account, Thunderbird's Exchange AutoDiscover lookup also queried the domain's AutoDiscover service over plain HTTP. Due to a bug, that unencrypted request included the credentials the user had entered, allowing a network attacker to obtain the user's password. This vulnerability was fixed in Thunderbird 158.0.1 and Thunderbird 153.5.1.
Weakness: CWE-523
Which versions are affected by CVE-2026-113866?
How do I fix CVE-2026-113866?
Upgrade to a fixed version.
Is CVE-2026-113866 being exploited?
There is no known exploitation of CVE-2026-113866 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-113866, GHSA-6c7w-fhrm-qhj3, UBUNTU-CVE-2026-113866.