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.

Weakness

The product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers.

Potential Mitigations

• Use a well-vetted algorithm that is currently considered to be strong by experts in the field, and select well-tested implementations with adequate length seeds.
• In general, if a pseudo-random number generator is not advertised as being cryptographically secure, then it is probably a statistical PRNG and should not be used in security-sensitive contexts.
• Pseudo-random number generators can produce predictable numbers if the generator is known and the seed can be guessed. A 256-bit seed is a good starting point for producing a “random enough” number.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/112.html
• https://cwe.mitre.org/data/definitions/485.html
• https://cwe.mitre.org/data/definitions/59.html

References

• https://access.redhat.com/security/cve/cve-2025-13402
• https://aur.archlinux.org/packages/rnp
• https://bugzilla.redhat.com/show_bug.cgi?id=2415863
• https://github.com/rnpgp/rnp/commit/7bd9a8dc356aae756b40755be76d36205b6b161a
• https://github.com/rnpgp/rnp/releases/tag/v0.18.1
• https://launchpad.net/ubuntu/+source/rnp
• https://open.ribose.com/advisories/ra-2025-11-20/
• https://packages.gentoo.org/packages/dev-util/librnp