Apache Struts is affected by CVE-2016-3081, rated 8.1 (high). CISA lists it as a Known Exploited Vulnerability, added on 2026-10-08, which means attacks against it have been observed.
What the flaw is
The NIST National Vulnerability Database describes it as follows:
Apache Struts 2.3.19 to 2.3.20.2, 2.3.21 to 2.3.24.1, and 2.3.25 to 2.3.28, when Dynamic Method Invocation is enabled, allow remote attackers to execute arbitrary code via method: prefix, related to chained expressions.
At a glance
| Field | Detail |
|---|---|
| CVE | CVE-2016-3081 |
| Affected product | Apache Struts |
| Weakness | CWE-77 (Command Injection) |
| CVSS | 8.1 HIGH — CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H |
| Added to CISA KEV | 2026-10-08 |
| Federal remediation due | 2026-10-11 |
| Known ransomware use | Unknown |
What defenders should do
- CISA required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
- Patch: apply the fixed release from Apache; check the vendor advisory linked below for the exact versions.
- Inventory: identify every instance of Apache Struts, prioritising internet-facing ones.
- Hunt: review access and application logs on exposed instances for activity predating the patch, and treat unpatched internet-facing instances as potentially compromised.
