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Fencer Intel
critical 9.1

CVE-2026-102946 json

joserfc: JWS signature verification bypass via empty signatures array in jws.deserialize_json

published 25d ago modified 25d ago also EUVD-2026-102310

cvss
9.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 1%
public exploits
0
none known

Summary

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.7.4, joserfc.jws.deserialize_json() accepts a JWS General JSON Serialization with an empty signatures array as authenticated. The verify_general_json() loop performs no iterations for the empty array and returns success because no signature check failed, allowing an attacker without a signing key to supply an arbitrary payload that relying applications may treat as authentic. The issue affects the General JSON Serialization path; compact JWS and JWT decoding, Flattened JSON serialization, and JWE JSON processing do not follow this vulnerable path. This issue is fixed in version 1.7.4.

Patch / fix

  • hsiaoming joserfc 1.7.4
  • joserfc Debian 14 1.7.4-1

debian advisories DEBIAN-CVE-2026-102946

  • python-joserfc openSUSE Tumbleweed 1.7.7-1.1
  • python-joserfc openSUSE Leap 16.0 1.1.0-bp160.5.1

opensuse advisories openSUSE-SU-2026:12204-1openSUSE-SU-2026:22136-1

Is CVE-2026-102946 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2026-102946 updated cvss 7.5

joserfc: joserfc: Signature verification bypass via empty signatures array

  • Red Hat Lightspeed Core lightspeed-core/lightspeed-stack-rhel9 Red Hat Migration Toolkit for Applications 8 mta/mta-solution-server-rhel9
    affected: workaround, no fix available
  • Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-agentic-sandbox-rhel9
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Ansible Automation Platform 2 ansible-automation-platform-26/lightspeed-chatbot-rhel9, ansible-automation-platform-27/lightspeed-chatbot-rhel9 Red Hat Enterprise Linux command line assistant rhel-cla/rhel-knowledge-bridge-rhel10 Red Hat OpenShift Virtualization 4 container-native-virtualization/ocp-virt-validation-checkup-rhel9
    affected: workaround, no fix available
  • Red Hat Satellite 6.18 satellite/foreman-mcp-server-rhel9 1793272276
    fixed: vendor fix RHSA-2026:92667
  • Red Hat Satellite 6.19 satellite/foreman-mcp-server-rhel9 1793272279
    fixed: vendor fix RHSA-2026:92666
  • Red Hat Exploit Intelligence exploit-intelligence/vulnerability-analysis-rhel9
    not affected: vulnerable code 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
total
Assessed
25d ago

Exploit prediction

0.12% chance of exploitation in the next 30 days, higher than 1% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/authlib/joserfc/security/advisories/GHSA-4pp3-559j-c5c2 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

  • authlib joserfc

Classification

Weakness
  • CWE-290 Authentication Bypass by Spoofing
  • CWE-345 Insufficient Verification of Data Authenticity
  • CWE-347 Improper Verification of Cryptographic Signature

References

Sources

Fencer Intel 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.