How severe is CVE-2025-27533?

CVE-2025-27533 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

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

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2025-27533?

O3 pinpoints whether CVE-2025-27533 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

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 8.6%, placing it in the 94th 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 March 14, 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

CVE-2025-27533

HIGH

Apache ActiveMQ: Unchecked buffer length can cause excessive memory allocation

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

Published

May 7, 2025

Updated

Mar 14, 2026

Affected

8 pkgs

Patched

8 / 8

Exploits

2 known

EPSS Exploitation Probability

via FIRST.org ↗

8.6%probability of exploitation in next 30 days

Lower Risk94th percentile+6.34%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

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

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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2025-27533 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2025-27533. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

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

O3 Security · Impact-Aware SCA

Is CVE-2025-27533 in your dependencies?

O3 detects CVE-2025-27533 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works