CVE-2023-46604
CVE-2023-46604 is a security flaw in Apache ActiveMQ, software that passes messages between business applications. Attackers can run their own code on Apache ActiveMQ. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 2 Nov 2023, and says ransomware gangs have used it.[1]
Apache ActiveMQ 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. Fixed in version 5.18.3, 5.17.6, 5.16.7 and 5.15.16.
Description
CISA calls it a deserialization of untrusted data in Apache ActiveMQ. In its words: “Apache ActiveMQ contains a deserialization of untrusted data vulnerability that may allow a remote attacker with network access to a broker to run shell commands by manipulating serialized class types in the OpenWire protocol to cause the broker to instantiate any class on the classpath.”[1]
The CVE record adds: “The Java OpenWire protocol marshaller is vulnerable to Remote Code Execution. This vulnerability may allow a remote attacker with network access to either a Java-based OpenWire broker or client to run arbitrary shell commands by manipulating serialized class types in the OpenWire protocol to cause either the client or the broker (respectively) to instantiate any class on the classpath. Users are recommended to upgrade both brokers and clients to version 5.15.16, 5.16.7, 5.17.6, or 5.18.3 which fixes this issue.”[2]
The underlying weakness is deserialization of untrusted data (CWE-502), in MITRE’s list of common software weaknesses.
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record lists these fixed versions: in each line, everything before the version shown is affected.[2]
| Product | Fixed in |
|---|---|
| Apache ActiveMQ | 5.18.3 |
| Apache ActiveMQ | 5.17.6 |
| Apache ActiveMQ | 5.16.7 |
| Apache ActiveMQ | 5.15.16 |
| Apache ActiveMQ Legacy OpenWire Module | 5.18.3 |
| Apache ActiveMQ Legacy OpenWire Module | 5.17.6 |
| Apache ActiveMQ Legacy OpenWire Module | 5.16.7 |
| Apache ActiveMQ Legacy OpenWire Module | 5.15.16 |
Most families won’t have Apache ActiveMQ; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 2 Nov 2023, 6 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 23 Nov 2023 to fix it.[1] CISA says ransomware gangs have used it.
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 over 99%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
Apache has published a fix or advice.[3] CISA’s required action: “Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.”[1]
- Check whether you use it.Apache ActiveMQ 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 (fixed in version 5.18.3, 5.17.6, 5.16.7 and 5.15.16), or not in use. CISA gave US government agencies until 23 Nov 2023 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 9.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks, noting that ransomware gangs have used it.[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 over 99%.[4] |
See also
Other Apache ActiveMQ flaws
- CVE-2026-34197: improper input validation ·
- CVE-2016-3088: improper input validation ·
Other Apache flaws
- CVE-2016-3081, Apache Struts: command injection ·
- CVE-2026-34486, Apache Tomcat: missing encryption of sensitive data ·
- 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 deserialization of untrusted data flaws
- CVE-2021-23758, Ajax.NET Professional: deserialization of untrusted data ·
- CVE-2026-63077, JetBrains TeamCity: deserialization of untrusted data ·
- CVE-2026-50522, Microsoft SharePoint: deserialization of untrusted data ·
- CVE-2026-58644, Microsoft SharePoint: deserialization of untrusted data ·
- CVE-2026-45659, Microsoft SharePoint Server: deserialization of untrusted data ·
Every Apache flaw on CISA’s list · Everything added in November 2023
References
- ^ Cybersecurity and Infrastructure Security Agency. “Apache ActiveMQ Deserialization of Untrusted Data Vulnerability”. Known Exploited Vulnerabilities Catalog, added 2 Nov 2023.
- ^ National Institute of Standards and Technology. “CVE-2023-46604 Detail”. National Vulnerability Database, published 27 Oct 2023.
- ^ Apache. Advisories and fixes: activemq.apache.org.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 1.000, percentile 100.0, 31 Oct 2026.
- CVE Program. “CVE-2023-46604”. 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.