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Python CVE-2026-39373

| EUVD-2026-19911 MEDIUM
Improper Handling of Highly Compressed Data (Data Amplification) (CWE-409)
2026-04-07 GitHub_M GHSA-fjrm-76x2-c4q4
5.3
CVSS 3.1
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CVSS VectorNVD

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

Lifecycle Timeline

4
Patch available
Apr 16, 2026 - 05:29 EUVD
1.5.7
EUVD ID Assigned
Apr 07, 2026 - 20:16 euvd
EUVD-2026-19911
Analysis Generated
Apr 07, 2026 - 20:16 vuln.today
CVE Published
Apr 07, 2026 - 19:35 nvd
MEDIUM 5.3

Blast Radius

ecosystem impact
† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth
  • 20 pypi packages depend on jwcrypto (15 direct, 5 indirect)

Ecosystem-wide dependent count for version 1.5.6.

DescriptionNVD

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.

AnalysisAI

Memory exhaustion in JWCrypto before 1.5.7 allows unauthenticated remote attackers to cause denial of service on memory-constrained systems by sending crafted JWE tokens with ZIP compression that decompress to approximately 100MB despite remaining under the 250KB input size limit. The vulnerability exploits incomplete validation in the upstream CVE-2024-28102 patch, which restricted input token size but failed to enforce decompressed output limits.

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CVE-2026-39373 vulnerability details – vuln.today

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