medium5.3
CVE-2026-39373
JWCrypto implements JWK, JWS, and JWE specifications using python-cryptography.
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | jwcrypto | <= 1.5.6 | 1.5.7 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Latchset | Jwcrypto | before 1.5.7 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-fjrm-76x2-c4q4
- https://github.com/latchset/jwcrypto/security/advisories/GHSA-fjrm-76x2-c4q4
- https://nvd.nist.gov/vuln/detail/CVE-2026-39373
- https://github.com/latchset/jwcrypto/commit/25db861d8b29434838669a94a843af03d29ea6ed
- https://github.com/latchset/jwcrypto/releases/tag/v1.5.7
- https://github.com/pypa/advisory-database/tree/main/vulns/jwcrypto/PYSEC-2026-70.yaml