CVE-2026-39373
MediumCVSS 5.3Exploitation Probability (EPSS)
Low risk22th percentile - higher than 22% of all known CVEs
Summary
JWCrypto before 1.5.7 does not validate decompressed output size in JWE tokens with ZIP compression. An attacker can send a small token (under 250KB) that decompresses to about 100MB, causing server memory exhaustion.
Risk Assessment
An unauthenticated attacker can cause memory exhaustion on memory-constrained systems, leading to denial of service (DoS).
Recommendation
Update JWCrypto to version 1.5.7 or later.
Original NVD description (English source)
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.