This page tracks the Ubuntu fix status. The vulnerability itself is described on the main CVE page.
View CVE-2026-91768 →
UBUNTU-CVE-2026-91768
The IPv6 branch of the FastCGI client access check compares only the first 12 bytes of a 16-byte IPv6 address, so listen.allowed_clients matches on a...
Original description
The description as published by the source.
The IPv6 branch of the FastCGI client access check compares only the first 12 bytes of a 16-byte IPv6 address, so listen.allowed_clients matches on a /96 prefix instead of the exact address. An attacker who can source an address sharing the first 96 bits with an allowed one passes the check and reaches the FastCGI endpoint.
Source: OSV.dev (Open Source Vulnerabilities) OSV
Affected packages
Ubuntu:Pro:14.04:LTS
php5
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:16.04:LTS
php7.0
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:18.04:LTS
php7.2
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:20.04:LTS
php7.4
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:22.04:LTS
php8.1
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:24.04:LTS
php8.3
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:26.10
php8.5
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:26.04:LTS
php8.5
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
References
- report ubuntu.com
- report cve.org
- report github.com
- report github.com