CVE-2018-5163: Canonical Ubuntu Linux

High severity, CVSS 8.1. EPSS: 2.1% chance of exploitation in the next 30 days.

If a malicious attacker has used another vulnerability to gain full control over a content process, they may be able to replace the alternate data resources stored in the JavaScript Start-up Bytecode Cache (JSBC) for other JavaScript code. If the parent process then runs this replaced code, the executed script would be run with the parent process' privileges, escaping the sandbox on content processes. This vulnerability affects Firefox < 60.

Affected products

• Canonical Ubuntu Linux: version 14.04 only; version 16.04 only; version 17.10 only; version 18.04 only
• Mozilla Firefox: before 60.0 (fixed in 60.0)

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