Medium
python-jwcrypto — security advisory
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.
- Products
- python-jwcrypto
- Affected versions
- 0.2.1-1, 0.3.2-1, 0.4.2-1, 0.6.0-1, 0.6.0-2, 0.8.0-1, 1.0.0-2, 1.1.0-1, 1.5.4-1, 1.5.6-1, 1.5.6-1.1, 1.5.6-1.2
- Fixed versions
- Not specified
- CVEs
- CVE-2026-39373
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 03:01 UTC · Revision 1
Source evidence
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.
osv:UBUNTU-CVE-2026-39373
python-jwcrypto
Fixed versions: Not specified
python-jwcrypto
Fixed versions: Not specified
python-jwcrypto
Fixed versions: Not specified
python-jwcrypto
Fixed versions: Not specified
python-jwcrypto
Fixed versions: Not specified
python-jwcrypto
Fixed versions: Not specified
python-jwcrypto
Fixed versions: Not specified
python-jwcrypto
Fixed versions: Not specified
Complete source record
{
"id": "db9584b5298e50eded2097ea9881778a172c41edd9b3273e1739fe5283659ee8",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-39373",
"method": "structured",
"payload": {
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"title": "UBUNTU-CVE-2026-39373",
"summary": "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.",
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"modified": "2026-10-17T13:00:02.728272245Z",
"provider": "osv",
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"references": [
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"https://www.cve.org/CVERecord?id=CVE-2026-39373",
"https://github.com/latchset/jwcrypto/security/advisories/GHSA-fjrm-76x2-c4q4"
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"source_id": "core-osv",
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"published_at": "2026-04-07T20:16:00+00:00"
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