CVE-2025-13470

In RNP version 0.18.0 a refactoring regression causes the symmetric 
session key used for Public-Key Encrypted Session Key (PKESK) packets to
 be left uninitialized except for zeroing, resulting in it always being 
an all-zero byte array.

Any data encrypted using public-key encryption 
in this release can be decrypted trivially by supplying an all-zero 
session key, fully compromising confidentiality.

The vulnerability affects only public key encryption (PKESK packets).  Passphrase-based encryption (SKESK packets) is not affected.

Root cause: Vulnerable session key buffer used in PKESK packet generation.



The defect was introduced in commit `7bd9a8dc356aae756b40755be76d36205b6b161a` where initialization 
logic inside `encrypted_build_skesk()` only randomized the key for the 
SKESK path and omitted it for the PKESK path.