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Fencer Intel
critical 9.8

CVE-2026-71253 json

Apache Johnzon: ClassConverter loads & static-initializes an attacker-named class from untrusted JSON

published 23d ago modified 22d ago also EUVD-2026-104193

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 32%
public exploits
0
none known

Summary

Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection') vulnerability in Apache Johnzon.

ClassConverter loads & static-initializes an attacker-named class from untrusted JSON.

This issue affects Apache Johnzon: from 1.0.0 before 2.2.0.

Users are recommended to upgrade to version 1.3.1 (javax namespace) or 2.2.0 (jakarta specification namespace), which fixes the issue.

Patch / fix

  • maven org.apache.johnzon:johnzon-mapper 1.3.1, 2.2.0
  • Apache Software Foundation Apache Johnzon 1.3.1, 2.2.0

Is CVE-2026-71253 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

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-2026-71253 updated cvss 8.1

org.apache.johnzon/johnzon-mapper: Apache Johnzon: Arbitrary code execution via unsafe class loading

  • Red Hat Fuse 7 johnzon-mapper 1.1.10
    affected: workaround, no fix planned “Out of support scope”

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
none
Automatable
yes
Technical impact
total
Assessed
22d ago

Exploit prediction

0.38% chance of exploitation in the next 30 days, higher than 32% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CISA ADP 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
maven org.apache.johnzon:johnzon-mapper
>=2.0.0, <2.2.0
>=1.0.0, <1.3.1
2.2.0
1.3.1

Affected products

  • Apache Software Foundation Apache Johnzon

Classification

Weakness
  • CWE-470 Use of Externally-Controlled Input to Select Classes or Code

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.