CVE-2026-19429

Jenkins FilePath.untarFrom() does not validate symlink targets in extracted TAR archives, even in versions patched for CVE-2026-33001 and CVE-2026-70427. An authenticated attacker with job configuration privileges can include a malicious archive in a build step that creates workspace symlinks pointing to arbitrary files on the Jenkins controller. By reading the secrets directory, the attacker obtains the cryptographic keys used to sign remember-me cookies, forges a valid administrator session cookie without any admin interaction, and gains access to the Script Console for remote code execution. Jenkins 2.576 is additionally affected by a bypass of the CVE-2026-70427 blank-name check via Unicode zero-width characters (U+200B, U+200C, U+200D, U+2060, U+00AD), which Java's String.isBlank() does not recognize as whitespace.