How severe is CVE-2025-27533?

No CVSS score has been assigned to CVE-2025-27533 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-27533?

CVE-2025-27533 affects the following packages: org.apache.activemq:activemq-openwire-legacy (Maven), org.apache.activemq:activemq-client (Maven), org.apache.activemq:activemq-openwire-legacy (Maven), org.apache.activemq:activemq-openwire-legacy (Maven), org.apache.activemq:activemq-openwire-legacy (Maven), org.apache.activemq:activemq-client (Maven), org.apache.activemq:activemq-client (Maven), org.apache.activemq:activemq-client (Maven). Ecosystems affected: Maven.

How do I fix CVE-2025-27533?

Update org.apache.activemq:activemq-openwire-legacy to 5.16.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-27533 is resolved across your whole dependency graph.

How do I detect CVE-2025-27533 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.activemq:activemq-openwire-legacy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-27533 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2025-27533 actively exploited in the wild?

Yes. There are 2 known exploit references for CVE-2025-27533, including 1 documented proof-of-concept exploit on Exploit-DB. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2025-27533?

CVE-2025-27533 has an EPSS (Exploit Prediction Scoring System) score of 9.1%, placing it in the 95th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-27533?

CVE-2025-27533 is classified as CWE-789 (CWE-789). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2025-27533 published, and has it been updated?

CVE-2025-27533 was published on May 7, 2025 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

Not in CISA KEV

CVE-2025-27533 — activemq-openwire-legacy

Fix: apache/activemq@fc4372b

CVE-2025-27533 is a CWE-789 vulnerability in org.apache.activemq:activemq-openwire-legacy. 2 public exploit or proof-of-concept references are indexed, so weaponization risk is real. A fix is available for org.apache.activemq:activemq-openwire-legacy — see the affected versions and patch details below.

Apache ActiveMQ: Unchecked buffer length can cause excessive memory allocation

Also known asBIT-activemq-2025-27533GHSA-whxr-3p84-rf3c

Published

May 7, 2025

Updated

Oct 28, 2026

Affected

8 pkgs

Patched

8 / 8

Exploits

2 known

Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-27533.

EPSS Exploitation Probability

via FIRST.org ↗

9.1%probability of exploitation in next 30 days

Lower Risk+0.15%

Lower risk than most CVEs95th percentile — riskier than 95% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

8 pkgs affected

☕org.apache.activemq:activemq-openwire-legacy☕org.apache.activemq:activemq-client☕org.apache.activemq:activemq-openwire-legacy☕org.apache.activemq:activemq-openwire-legacy☕org.apache.activemq:activemq-openwire-legacy☕org.apache.activemq:activemq-client☕org.apache.activemq:activemq-client☕org.apache.activemq:activemq-client

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Memory Allocation with Excessive Size Value vulnerability in Apache ActiveMQ.

During unmarshalling of OpenWire commands the size value of buffers was not properly validated which could lead to excessive memory allocation and be exploited to cause a denial of service (DoS) by depleting process memory, thereby affecting applications and services that rely on the availability of the ActiveMQ broker when not using mutual TLS connections. This issue affects Apache ActiveMQ: from 6.0.0 before 6.1.6, from 5.18.0 before 5.18.7, from 5.17.0 before 5.17.7, before 5.16.8. ActiveMQ 5.19.0 is not affected.

Users are recommended to upgrade to version 6.1.6+, 5.19.0+, 5.18.7+, 5.17.7, or 5.16.8 or which fixes the issue.

Existing users may implement mutual TLS to mitigate the risk on affected brokers.

Affected Packages

8 total 8 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.apache.activemq:activemq-openwire-legacy`	all versions	5.16.8`org.apache.activemq:activemq-openwire-legacy:5.16.8`
☕Maven	`org.apache.activemq:activemq-client`	all versions	5.16.8`org.apache.activemq:activemq-client:5.16.8`
☕Maven	`org.apache.activemq:activemq-openwire-legacy`	≥ 5.17.0&&< 5.17.7	5.17.7`org.apache.activemq:activemq-openwire-legacy:5.17.7`
☕Maven	`org.apache.activemq:activemq-openwire-legacy`	≥ 5.18.0&&< 5.18.7	5.18.7`org.apache.activemq:activemq-openwire-legacy:5.18.7`
☕Maven	`org.apache.activemq:activemq-openwire-legacy`	≥ 6.0.0&&< 6.1.6	6.1.6`org.apache.activemq:activemq-openwire-legacy:6.1.6`
☕Maven	`org.apache.activemq:activemq-client`	≥ 5.17.0&&< 5.17.7	5.17.7`org.apache.activemq:activemq-client:5.17.7`

Affected Products

1 product · 4 configurations

Application

activemqapache

≥ 6.0.0 && < 6.1.6

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

EDB-52288remotemultiple

Apache ActiveMQ 6.1.6 - Denial of Service (DOS)

by Abdualhadi khalifa · May 9, 2025

Exploit-DB Source

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.activemq:activemq-openwire-legacy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.apache.activemq:activemq-openwire-legacy to 5.16.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-27533 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Product	Fixed in	Advisory
Red Hat AMQ Broker 7.13.2	`activemq-openwire-legacy`	RHSA-2025:17567

Frequently Asked Questions

Memory Allocation with Excessive Size Value vulnerability in Apache ActiveMQ. During unmarshalling of OpenWire commands the size value of buffers was not properly validated which could lead to excessive memory allocation and be exploited to cause a denial of service (DoS) by depleting process memory, thereby affecting applications and services that rely on the availability of the ActiveMQ broker when not using mutual TLS connections. This issue affects Apache ActiveMQ: from 6.0.0 before 6.1.6, from 5.18.0 before 5.18.7, from 5.17.0 before 5.17.7, before 5.16.8. ActiveMQ 5.19.0 is not affected