CVE-2025-27625: Jenkins Open Redirect vulnerability

Various features in Jenkins redirect users to partially user-controlled URLs inside Jenkins. To prevent open redirect vulnerabilities, Jenkins limits redirections to safe URLs (neither absolute nor scheme-relative/network-path reference).

In Jenkins 2.499 and earlier, LTS 2.492.1 and earlier, redirects starting with backslash (\) characters are considered safe.

This allows attackers to perform phishing attacks by having users go to a Jenkins URL that will forward them to a different site, because browsers interpret these characters as part of scheme-relative redirects.

Jenkins 2.500, LTS 2.492.2 considers redirects to URLs starting with backslash (\) characters to be unsafe, rejecting such redirects.