CISA Sets Oct 11 Deadline for Federal Agencies to Mitigate Apache Struts CVE-2016-3081 Risk

The Cybersecurity and Infrastructure Security Agency added a long-standing Apache Struts command injection flaw to its Known Exploited Vulnerabilities catalog. This action mandates immediate risk mitigation for federal civil executive branch systems by a specific deadline.

What happened

CISA published CVE-2016-3081 in the KEV catalog on October 8, 2026. The entry sets a federal due date of October 11, 2026, for agencies to address the issue. The vulnerability allows remote attackers to execute arbitrary code on affected systems. It occurs when the Dynamic Method Invocation feature is enabled in Apache Struts. Attackers exploit the flaw using the method: prefix in chained expressions.

According to the National Vulnerability Database, the issue impacts Apache Struts versions 2.3.19 to 2.3.20.2, 2.3.21 to 2.3.24.1, and 2.3.25 to 2.3.28. The NVD assigns the vulnerability a CVSS score of 8.1, rating it as high severity. The weakness is associated with CWE-77, indicating improper neutralization of special elements used in an OS command.

CISA notes that ransomware use of this vulnerability is currently unknown. However, the inclusion in the KEV catalog signals that the agency considers the threat active and significant. The required action for stakeholders is to apply mitigations in accordance with vendor instructions. If mitigations are unavailable, agencies must discontinue use of the product. Stakeholders are also responsible for evaluating each asset's internet exposure.

Why it matters

The addition of CVE-2016-3081 to the KEV catalog triggers specific compliance requirements under CISA’s Binding Operational Directive 26-04. This directive prioritizes security updates based on risk. Federal agencies must ensure adherence to these patching guidelines to maintain compliance. Failure to meet the October 11 deadline may result in non-compliance findings.

For non-federal organizations, the listing serves as a critical warning. The vulnerability has been known for years, yet its presence in the KEV catalog indicates ongoing exploitation in the wild. Security teams should treat this as a high-priority item. The ability to execute arbitrary code remotely makes this a severe risk to system integrity and confidentiality. Organizations running affected versions of Apache Struts with Dynamic Method Invocation enabled are directly exposed.

Our take on the response

• Identify all instances of Apache Struts versions 2.3.19 through 2.3.28 in your environment.
• Check if Dynamic Method Invocation is enabled on these instances.
• Apply vendor-recommended mitigations immediately.
• If mitigation is not possible, discontinue use of the affected product.
• Ensure compliance with BOD 26-04 guidance for cloud services.
• Evaluate internet exposure for each asset to reduce attack surface.

What to do and how to stay safe: Apache Struts

• Inventory your application stack to locate any Apache Struts components running versions between 2.3.19 and 2.3.28.
• Verify whether Dynamic Method Invocation is enabled on these components, as this is the primary condition for exploitation.
• Review vendor documentation for specific mitigation steps and apply them to reduce the attack surface immediately.
• Monitor network traffic for unusual command execution patterns or signs of arbitrary code execution on exposed servers.

Step-by-step guide: Vulnerability Management Myths That Waste Your Time and Budget

General security guidance from the NetSec Tribune newsroom. It is not confirmed advice from the organisations named in this story.

Frequently asked questions

Which Apache Struts versions are affected by CVE-2016-3081?

Versions 2.3.19 to 2.3.20.2, 2.3.21 to 2.3.24.1, and 2.3.25 to 2.3.28 are affected when Dynamic Method Invocation is enabled.

What is the federal deadline for mitigating this vulnerability?

The federal due date is October 11, 2026.

Is this vulnerability associated with ransomware activity?

CISA lists ransomware use as unknown for this specific entry.