CVE-2018-1000027: Canonical Ubuntu Linux

High severity, CVSS 7.5. EPSS: 12.9% chance of exploitation in the next 30 days.

The Squid Software Foundation Squid HTTP Caching Proxy version prior to version 4.0.23 contains a NULL Pointer Dereference vulnerability in HTTP Response X-Forwarded-For header processing that can result in Denial of Service to all clients of the proxy. This attack appear to be exploitable via Remote HTTP server responding with an X-Forwarded-For header to certain types of HTTP request. This vulnerability appears to have been fixed in 4.0.23 and later.

Affected products

• Canonical Ubuntu Linux: version 14.04 only; version 16.04 only; version 17.10 only
• Debian Debian Linux: version 7.0 only; version 8.0 only; version 9.0 only
• Squid-Cache Squid: before 4.0.23 (fixed in 4.0.23)

Published 2018-02-09. Last modified 2026-06-17.