CVE-2026-39373: JWCrypto implements JWK, JWS, and JWE specifications using python-cryptography

Q: How do I fix CVE-2026-39373?

jwcrypto: upgrade to 1.5.7. Exact commands for each OS are on this page.

Q: Is CVE-2026-39373 being exploited?

CVE-2026-39373 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-39373 affect?

CVE-2026-39373 affects jwcrypto. Severity is medium (CVSS 5.3). 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

Q: How urgent is CVE-2026-39373?

Priority 34/100. Public exploit reference; Remotely exploitable, no login, no user action

This week

MEDIUM 5.3REMOTEUPGRADE

CVE-2026-39373 is a medium-severity flaw (CVSS 5.3) affecting jwcrypto. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 c

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 78%)
CISA exploited list	No
Weakness	CWE-409
Published	2026-04-07
Last modified	2026-07-24

Publisher (CNA): GitHub, Inc. · Vendor: latchset

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-07 20:16 UTCPublished CVE record published
2026-07-24 21:10 UTCUpdated Record last modified

latchset jwcrypto UPGRADE

Affected: < 1.5.7

Fixed in: 1.5.7

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy jwcrypto || rpm -q jwcrypto || jwcrypto --version

2. UPGRADE to 1.5.7 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade jwcrypto

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade jwcrypto

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-39373?

jwcrypto: upgrade to 1.5.7. Exact commands for each OS are on this page.

Is CVE-2026-39373 being exploited?

CVE-2026-39373 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-39373 affect?

CVE-2026-39373 affects jwcrypto. Severity is medium (CVSS 5.3). 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

How urgent is CVE-2026-39373?

Priority 34/100. Public exploit reference; Remotely exploitable, no login, no user action

Software pages

Python vulnerabilities

References

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