CVE-2018-18506: Canonical Ubuntu Linux

Medium severity, CVSS 5.9. EPSS: 2.2% chance of exploitation in the next 30 days.

When proxy auto-detection is enabled, if a web server serves a Proxy Auto-Configuration (PAC) file or if a PAC file is loaded locally, this PAC file can specify that requests to the localhost are to be sent through the proxy to another server. This behavior is disallowed by default when a proxy is manually configured, but when enabled could allow for attacks on services and tools that bind to the localhost for networked behavior if they are accessed through browsing. This vulnerability affects Firefox < 65.

Affected products

• Canonical Ubuntu Linux: version 14.04 only; version 16.04 only; version 18.04 only; version 18.10 only
• Debian Debian Linux: version 8.0 only; version 9.0 only
• Mozilla Firefox: before 65.0 (fixed in 65.0)
• Opensuse Leap: version 15.0 only; version 42.3 only
• Red Hat Enterprise Linux: version 8.0 only
• Red Hat Enterprise Linux Desktop: version 6.0 only; version 7.0 only
• Red Hat Enterprise Linux Eus: version 8.1 only; version 8.2 only; version 8.4 only; version 8.6 only
• Red Hat Enterprise Linux Server: version 6.0 only; version 7.0 only
• Red Hat Enterprise Linux Server Aus: version 7.6 only; version 8.2 only; version 8.4 only; version 8.6 only
• Red Hat Enterprise Linux Server Eus: version 7.6 only
• Red Hat Enterprise Linux Server Tus: version 7.6 only; version 8.2 only; version 8.4 only; version 8.6 only
• Red Hat Enterprise Linux Workstation: version 6.0 only; version 7.0 only

Published 2019-02-05. Last modified 2026-06-17.