CVE-2016-3081
CVE-2016-3081 is a security flaw in Apache Struts, a framework for building Java web applications. Attackers can run their own code on Apache Struts. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 8 Oct 2026.[1]
Apache Struts is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Apache has published a fix or advice.
Description
CISA calls it a command injection in Apache Struts. In its words: “Apache Struts contains a command injection vulnerability that could allow remote attackers to execute arbitrary code via method:prefix when Dynamic Method Invocation is enabled.”[1]
The CVE record adds: “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.”[2]
The underlying weakness is command injection (CWE-77), in MITRE’s list of common software weaknesses.
It scores 8.1 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Apache’s advisory has them[3]. CISA names the product as Apache Struts.
Most families won’t have Apache Struts; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 8 Oct 2026, 3,817 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 11 Oct 2026 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 97%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Apache has published a fix or advice.[3] CISA’s 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).”[1]
- Check whether you use it.Apache Struts is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 11 Oct 2026 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 8.1.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 97%.[4] |
See also
Other Apache Struts flaws
- CVE-2013-2251: improper input validation ·
- CVE-2020-17530: remote code execution ·
- CVE-2018-11776: remote code execution ·
- CVE-2017-9805: deserialization of untrusted data ·
- CVE-2017-5638: remote code execution ·
Other Apache flaws
- CVE-2026-34486, Apache Tomcat: missing encryption of sensitive data ·
- CVE-2026-34197, Apache ActiveMQ: improper input validation ·
- CVE-2024-38475, Apache HTTP Server: improper escaping of output ·
- CVE-2025-24813, Apache Tomcat: path equivalence ·
- CVE-2024-45195, Apache OFBiz: forced browsing ·
Other command injection flaws
- CVE-2026-105134, AhsayCBS: command injection ·
- CVE-2026-96951, Microsoft Windows: command injection ·
- CVE-2026-8037, Progress LoadMaster: command injection ·
- CVE-2025-29635, D-Link DIR-823X: command injection ·
- CVE-2026-22719, Broadcom VMware Aria Operations: command injection ·
Added the same day
- CVE-2023-22894, Strapi: cleartext storage of sensitive information ·
- CVE-2021-3199, ONLYOFFICE Docs: server path traversal ·
- CVE-2015-5477, ISC BIND: data processing errors ·
- CVE-2015-3306, ProFTPD: improper access control ·
Every Apache flaw on CISA’s list · Everything added in October 2026
References
- ^ Cybersecurity and Infrastructure Security Agency. “Apache Struts Command Injection Vulnerability”. Known Exploited Vulnerabilities Catalog, added 8 Oct 2026.
- ^ National Institute of Standards and Technology. “CVE-2016-3081 Detail”. National Vulnerability Database, published 26 Apr 2016.
- ^ Apache. Advisories and fixes: cwiki.apache.org, struts.apache.org.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.965, percentile 99.9, 31 Oct 2026.
- CVE Program. “CVE-2016-3081”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.