Quick answers
- Is CVE-2026-109782 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-109782 being exploited in the wild.
- How severe is CVE-2026-109782?
- Informational severity, published 13 October 2026.
- Which products and versions are affected?
- Mozilla Firefox ESR before 153.5; Mozilla Thunderbird before 153.5.
- Is there a fix for CVE-2026-109782?
- Yes: fixed in Firefox ESR 153.5, Thunderbird 153.5. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-109782 attacked?
- It is attacked over the network, in a web application.
- Am I affected by CVE-2026-109782?
- Check whether you run Mozilla Firefox ESR or 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: Firefox ESR 153.5, Thunderbird 153.5
Technical details
A mitigation bypass in the File Handling component of Firefox ESR and Thunderbird allows attackers to evade existing security controls. The vulnerability requires network access and likely user interaction (file download or handling). A fix is available in Firefox ESR 153.5 and Thunderbird 153.5.
Affected products
- Mozilla Firefox ESR before 153.5
- Mozilla Thunderbird before 153.5
Timeline
- 2026-10-13: disclosed