[ANN] CVE-2026-73635: Apache Struts: Unbounded growth of localized-text caches driven by the request locale - S2-074

Severity: moderate

Affected versions:
- Apache Struts (org.apache.struts:struts2-core) 2.0.0 through 2.3.37
- Apache Struts (org.apache.struts:struts2-core) 2.5.0 through 2.5.33
- Apache Struts (org.apache.struts:struts2-core) 6.0.0 through 6.10.0
- Apache Struts (org.apache.struts:struts2-core) 7.0.0 through 7.2.1

Description:
Allocation of resources without limits or throttling vulnerability in
Apache Struts. When no fixed locale is configured, the locale used for
localized-text lookups is taken from the incoming request, allowing an
unauthenticated remote client to cause the framework's internal
localized-text caches to grow without bound and exhaust the Java heap,
denying service to other users. Applications that configure a fixed locale
are not affected.

This issue affects Apache Struts: from 2.0.0 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:
Kuniyoshi Noguchi (野口 晋義), (@KuniNogu) (finder)

References:
https://cwiki.apache.org/confluence/display/WW/S2-074
https://www.cve.org/CVERecord?id=CVE-2026-73635


On behalf of the Apache Struts project
Łukasz Lenart