CVE-2017-5403: Mozilla Firefox

Critical severity, CVSS 9.8. EPSS: 1.7% chance of exploitation in the next 30 days.

When adding a range to an object in the DOM, it is possible to use "addRange" to add the range to an incorrect root object. This triggers a use-after-free, resulting in a potentially exploitable crash. This vulnerability affects Firefox < 52 and Thunderbird < 52.

Affected products

• Mozilla Firefox: before 52.0 (fixed in 52.0)
• Mozilla Thunderbird: before 52.0 (fixed in 52.0)

Published 2018-06-11. Last modified 2026-06-17.