JWCrypto implements JWK, JWS, and JWE specifications using python-cryptography. Prior to 1.5.7, an unauthenticated attacker can exhaust server memory by sending crafted JWE tokens with ZIP compression. The existing patch for CVE-2024-28102 limits input token size to 250KB but does not validate the decompressed output size. An unauthenticated attacker can cause memory exhaustion on memory-constrained systems. A token under the 250KB input limit can decompress to approximately 100MB. This vulnerability is fixed in 1.5.7.
The severity of this bug is wrong, it should be low. No attacker can cause unlimited memory exhaustion, the bug only highlighted that the amount of memory used culd not be finely controlled, but the previous fix did absolutely allow to limit memory use. This is a very low priority issue.