Critical severity · published Oct 19, 2026
CVE-2026-71253
Apache Johnzon: ClassConverter loads & static-initializes an attacker-named class from untrusted JSON
9.8
CVSS
0.4%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 32% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
AJ
Apache Johnzon · Apache Software Foundation
2.0.0 before 2.2.0; 1.0.0 before 1.3.1 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-71253
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-71253
github.com
https://github.com/apache/johnzon/commit/91e7b0d21d08d138944e2570691939739422a3d6
github.com
https://github.com/apache/johnzon/commit/dd3d00634c746a2173a2518e882e85e8a151bf30
lists.apache.org
https://lists.apache.org/thread.html/3vgm1yo2sn9yhkvvs9lc4ro01vl3zt68