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Fencer Vulns
medium 5.3

CVE-2026-39373 json

JWCrypto: JWE ZIP decompression bomb

published 2026-04-07 7 mo ago modified 2026-09-10 1 mo ago also EUVD-2026-19911 , GHSA-fjrm-76x2-c4q4 , PYSEC-2026-70

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 23%
public exploits
0
none known

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.

Patch / fix

  • pypi jwcrypto 1.5.7
  • jwcrypto_project jwcrypto 1.5.7
  • python-jwcrypto Debian 13 1.5.6-1.1~deb13u1
  • python-jwcrypto Debian 14 1.5.6-1.1

debian advisories DEBIAN-CVE-2026-39373

  • python3.12-django ansible automation platform developer 2.5, ansible automation platform 2.5 5.2.17-1.el8ap
  • python3.12-django ansible automation platform developer 2.6, ansible automation platform developer 2.5, ansible automation platform 2.6 +1 more 5.2.17-1.el9ap
  • python3.12-aiohttp ansible automation platform 2.5 3.14.3-1.el8ap
  • python3.12-aiohttp ansible automation platform 2.6, ansible automation platform 2.5 3.14.3-1.el9ap
  • python3.12-gitpython ansible automation platform 2.5 3.1.59-1.el8ap
  • python3.12-gitpython ansible automation platform 2.6, ansible automation platform 2.5 3.1.59-1.el9ap
  • automation-controller-cli ansible automation platform developer 2.5, ansible automation platform 2.5 4.6.32-1.el8ap
  • automation-controller-cli ansible automation platform developer 2.5, ansible automation platform 2.5 4.6.32-1.el9ap

red hat advisories RHSA-2026:59135RHSA-2026:59136RHSA-2026:19197RHSA-2026:19042RHSA-2026:13508RHSA-2026:13512

  • python-jwcrypto openSUSE Tumbleweed 1.5.7-2.1

opensuse advisories openSUSE-SU-2026:10576-1

  • python3-jwcrypto AlmaLinux 10 1.5.6-5.el10_2
  • python3-jwcrypto AlmaLinux 9 1.5.6-3.el9_8

almalinux advisories ALSA-2026:19042ALSA-2026:19197

  • python-jwcrypto Rocky Linux 10 1.5.6-5.el10_2
  • python-jwcrypto Rocky Linux 9 1.5.6-3.el9_8

rocky linux advisories RLSA-2026:19042RLSA-2026:19197

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-39373 updated cvss 7.5

JWCrypto: python-cryptography: python: JWCrypto: Memory exhaustion via crafted compressed JWE tokens

  • Red Hat Ansible Automation Platform 2 ansible-automation-platform-24/lightspeed-rhel8, ansible-automation-platform-25/lightspeed-rhel8, ansible-automation-platform-26/lightspeed-rhel9 Red Hat Enterprise Linux 7 python-jwcrypto Red Hat Enterprise Linux 8 python-jwcrypto, python3-jwcrypto
    affected: no fix available “Fix deferred”
  • Red Hat Ansible Automation Platform 2.5 for RHEL 8 python3.12-jwcrypto 1.5.7-1.el8ap, automation-controller-venv-tower 4.6.32-1.el8ap Red Hat Ansible Automation Platform 2.5 for RHEL 9 python3.12-jwcrypto 1.5.7-1.el9ap, automation-controller-venv-tower 4.6.32-1.el9ap
    fixed: vendor fix RHSA-2026:59135
  • Red Hat Ansible Automation Platform 2.6 ansible-automation-platform-26/gateway-rhel9 1783969842
    fixed: vendor fix RHSA-2026:42132
  • Red Hat Ansible Automation Platform 2.6 for RHEL 9 python3.12-jwcrypto 1.5.7-1.el9ap, automation-controller-venv-tower 4.7.16-1.el9ap
    fixed: vendor fix RHSA-2026:59136
  • Red Hat Enterprise Linux AppStream (v. 9) python-jwcrypto 1.5.6-3.el9_8, python3-jwcrypto 1.5.6-3.el9_8
    fixed: vendor fix RHSA-2026:19197
  • Red Hat Enterprise Linux AppStream (v. 10) python-jwcrypto 1.5.6-5.el10_2, python3-jwcrypto 1.5.6-5.el10_2
    fixed: vendor fix RHSA-2026:19042
  • Red Hat Ansible Automation Platform 2 python3.11-jwcrypto, ansible-automation-platform-26/controller-rhel9 Red Hat Ansible Automation Platform 2.5 for RHEL 8 receptor 1.6.4-2.el8ap, yamllint 1.38.0-1.el8ap, receptorctl 1.6.4-2.el8ap, ansible-lint 26.1.1-1.el8ap, ansible-core 2.16.18-1.el8ap, ansible-test 2.16.18-1.el8ap, +60 more Red Hat Ansible Automation Platform 2.5 for RHEL 9 receptor 1.6.4-2.el9ap, yamllint 1.38.0-1.el9ap, receptorctl 1.6.4-2.el9ap, ansible-lint 26.1.1-1.el9ap, ansible-core 2.16.18-1.el9ap, ansible-test 2.16.18-1.el9ap, +60 more Red Hat Ansible Automation Platform 2.6 ansible-automation-platform-26/hub-rhel9 1783979593, ansible-automation-platform-26/hub-web-rhel9 1783982443, ansible-automation-platform-26/receptor-rhel9 1783962464, ansible-automation-platform-26/mcp-tools-rhel9 1783920640, ansible-automation-platform-26/controller-rhel9 1783973764, ansible-automation-platform-26/de-minimal-rhel9 1783921549, +24 more Red Hat Ansible Automation Platform 2.6 for RHEL 9 receptor 1.6.4-2.el9ap, molecule 26.8.0-1.el9ap, yamllint 1.38.0-1.el9ap, receptorctl 1.6.4-2.el9ap, ansible-lint 26.1.1-1.el9ap, ansible-lint 26.8.0-1.el9ap, +89 more Red Hat Ansible Automation Platform 2.6 for RHEL 10 receptor 1.6.4-3.el10ap, molecule 26.8.0-1.el10ap, yamllint 1.38.0-2.el10ap, receptorctl 1.6.4-3.el10ap, ansible-lint 26.1.1-2.el10ap, ansible-lint 26.8.0-1.el10ap, +20 more
    not affected: vulnerable code not present
  • Red Hat Hardened Images python-cryptography
    not affected: component not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.31% chance of exploitation in the next 30 days, higher than 23% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/latchset/jwcrypto/security/advisories/GHSA-fjrm-76x2-c4q4 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
OSV 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected packages

ecosystem package affected fixed in
pypi jwcrypto
<1.5.7
1.5.7

Affected products

  • latchset jwcrypto

Classification

Weakness
  • CWE-409 Improper Handling of Highly Compressed Data (Data Amplification)

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.