Crypt::Age versions before 0.004 for Perl allow CPU exhaustion via an unbounded number of recipient…

Why it is Yellow

• CVSS 7.5 high
• Remotely exploitable without logging in

References

• https://metacpan.org/release/GETTY/Crypt-Age-0.004/changes
• http://www.openwall.com/lists/oss-security/2026/10/20/39

Original description

Crypt::Age versions before 0.004 for Perl allow CPU exhaustion via an unbounded number of recipient stanzas, each costing an X25519 scalar multiplication in unwrap_file_key. The header parser accepts any number of recipient stanzas, and unwrap_file_key tries every identity against every X25519 stanza. Each attempt runs a scalar multiplication, an HKDF and a ChaCha20-Poly1305 open. The header MAC cannot be checked first, because its key comes from the file key, which only a successful unwrap produces. Each stanza is 98 bytes of attacker-chosen header and buys one scalar multiplication per identity held, and the file is rejected only after every one of them has run. A caller reaches this through decrypt, decrypt_file or decrypt_filehandle whenever it decrypts a file it did not write.