5.3

CVE-2026-39373: JWCrypto: JWE ZIP decompression bomb

Analyzed
AliasesGHSA-fjrm-76x2-c4q4PYSEC-2026-70RHSA-2026:19042
Published 07-04-2026Last modified 07-04-2026

Vulnerability summary

CVE-2026-39373 is a medium (CVSS 5.3) vulnerability in latchset jwcrypto. EPSS estimates a 0.29% chance of exploitation in the next 30 days, higher than 22.1% of scored vulnerabilities. 1 public exploit is recorded.

Priority
Routine

Not severe (CVSS 5.3, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
5.3/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.29%
0%100%
Low · -0.14 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits1github

Advisory lineage

Upstream 0 · Downstream 4 · Related 1
RHSA-2026:13508RHSA-2026:13512RHSA-2026:59135RHSA-2026:59136CGA-G384-JWHX-HWW5

Timeline

  1. 07-04-2026
    PublishedVulnerability first disclosed.
  2. 07-04-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

8 scores · 8 sources · 1 version

EPSS trend

Probability

0.29%

Chance of exploitation in the next 30 days

Percentile

22%

Versus all other CVEs

30-day change

Decrease -0.14 pp

From 0.43% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

1 found
  • githubUnverified

    Jwcrypto

    Maturity: poc

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Chainguard12 products
  • authentik-2025.12< 2025.12.4-r5
  • authentik-2026.2< 2026.2.1-r5
  • authentik-fips-2025.12< 2025.12.4-r4
  • authentik-fips-2026.2< 2026.2.1-r4
  • awx< 24.6.1-r42
Wolfi5 products
  • py3-jwcrypto< 1.5.7-r0
  • py3.10-jwcrypto< 1.5.7-r0
  • py3.11-jwcrypto< 1.5.7-r0
  • py3.12-jwcrypto< 1.5.7-r0
  • py3.13-jwcrypto< 1.5.7-r0
Redhat2 products
  • python-jwcrypto< 0:1.5.6-5.el10_2 | < 0:1.5.6-3.el9_8
  • python3-jwcrypto< 0:1.5.6-5.el10_2 | < 0:1.5.6-3.el9_8
Debian1 product
  • python-jwcryptoAll versions (No fix recorded) | < 1.5.6-1.1~deb13u1 | < 1.5.6-1.1
Latchset1 product
Opensuse1 product
  • python-jwcrypto&distro=openSUSE Tumbleweed< 1.5.7-2.1
PyPI1 product
  • jwcrypto< 1.5.7
Ubuntu1 product
  • python-jwcryptoAll versions (No fix recorded)

8 vendors · 24 products

References

18 links
Show all 18 references