CVE-2026-39373
JWCrypto: JWE ZIP decompression bomb
5.3
MEDIUM
CVSS 3.1
EPSS 0.10%
Description
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.
How to fix CVE-2026-39373
To remediate CVE-2026-39373, upgrade the affected package to a fixed version below.
- —no fix listed
- —no fix listed
- —upgrade to 1.5.7 or later
Is CVE-2026-39373 being exploited?
Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.
Affected packages (3)
- from 0
- from 0, <= 1.5.6
- from 0, < 1.5.7
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |