CVE-2025-27533: 
Java vulnerability analysis and mitigation

A Memory Allocation with Excessive Size Value vulnerability (CVE-2025-27533) was discovered in Apache ActiveMQ on May 6, 2025. The vulnerability affects multiple versions of Apache ActiveMQ: 6.0.0 before 6.1.6, 5.18.0 before 5.18.7, 5.17.0 before 5.17.7, and versions before 5.16.8, while version 5.19.0 is not affected (NVD, SecurityOnline).

The vulnerability stems from improper validation of buffer size values during the unmarshalling of OpenWire commands. This oversight in input validation could lead to excessive memory allocation when processing specially crafted messages. The issue has been assigned a CVSS 4.0 Base Score of 6.9 (MEDIUM) with the vector string CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/AU:Y/R:A/V:D/RE:M/U:Red and is classified under CWE-789: Memory Allocation with Excessive Size Value (Wiz, NVD).

The primary impact of this vulnerability is the potential for denial of service (DoS) attacks through process memory depletion. When exploited, it can affect applications and services that depend on the availability of the ActiveMQ broker, particularly in environments not using mutual TLS connections. This can lead to service disruption and system unavailability (Wiz, SecurityOnline).

Apache has released patched versions to address this vulnerability. Users are strongly recommended to upgrade to version 6.1.6+, 5.19.0+, 5.18.7+, 5.17.7, or 5.16.8. For environments unable to upgrade immediately, implementing mutual TLS on ActiveMQ brokers serves as an effective mitigation measure (OpenWall, SecurityOnline).