[ANN] CVE-2026-73633: Apache Struts: Unbounded read of a JSON request body - S2-072

Severity: moderate

Affected versions:
- Apache Struts (org.apache.struts:struts2-json-plugin) 2.1.8 through 2.3.37
- Apache Struts (org.apache.struts:struts2-json-plugin) 2.5.0 through 2.5.33
- Apache Struts (org.apache.struts:struts2-json-plugin) 6.0.0 through 6.10.0
- Apache Struts (org.apache.struts:struts2-json-plugin) 7.0.0 through 7.2.1

Description:
Uncontrolled resource consumption vulnerability in the JSON plugin of
Apache Struts. When an application is configured to populate actions from a
JSON request body, the plugin reads that body into memory without bounding
how much it will accept, so a single request can exhaust the heap and deny
service to other users. The plugin's configurable JSON input length limit
does not bound this read. The JSON plugin is an optional component;
applications that do not use it, or use it without enabling JSON
request-body handling, are not affected.

This issue affects Apache Struts: from 2.1.8 through 2.3.37, from 2.5.0
through 2.5.33, from 6.0.0 through 6.10.0, from 7.0.0 through 7.2.1.

Users are recommended to upgrade to version 6.11.0 or 7.3.0, which fixes
the issue.

Credit:
Michael Mullins (finder)

References:
https://cwiki.apache.org/confluence/display/WW/S2-072
https://www.cve.org/CVERecord?id=CVE-2026-73633


On behalf of the Apache Struts project
Łukasz Lenart