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.

Rejected reason: This CVE ID has been rejected or withdrawn by its CVE Numbering Authority.

Jenkins FilePath.untarFrom() (all versions) validates symlink destinations but not targets, bypassing CVE-2026-33001. Any user with Item/Build access triggers tar extraction via POST /job/{name}/build, writing persistent symlinks into the tool cache. Symlinks to secrets/master.key, hudson.util.Secret, credentials.xml, and users/*/config.xml read via GET /job/{name}/lastBuild/consoleText enable offline AES decryption of all credentials and admin API tokens without bcrypt cracking, achieving RCE.