The flaw exists in Bouncy Castle for Java implementations prior to the specified versions, where the length of an OpenPGP user‑attribute subpacket is not limited except by the maximum size of the JVM heap. An attacker delivering a crafted subpacket can force the library to attempt allocation of an arbitrarily large block of memory, leading to an out‑of‑memory condition that can crash the application or consume all available resources, thereby denying service. This is a classic memory allocation weakness, identified as CWE‑789.

Affected products include Bouncy Castle for Java (bcpg 1.0‑X series) before version 1.85, the Long Term Support (LTS) Java library before 2.73.12, and the Bouncy Castle for Java FIPS (BC‑FJA) library before bcpg‑fips 1.0.13, 2.0.13, and 2.1.13. These libraries are used in many Java applications that handle OpenPGP data, such as security tools, email clients, or communication platforms relying on Bouncy Castle for cryptographic operations.

The CVSS base score of 8.7 classifies the vulnerability as high severity. Exploitation requires only the ability to deliver a crafted OpenPGP packet to a Java process that employs an unpatched Bouncy Castle library, making the attack relatively straightforward once the target is identified. EPSS is not available, but the absence of a KEV listing does not diminish the risk, particularly because many organizations deploy Bouncy Castle in complex services exposed to external inputs. An out‑of‑memory attack can terminate services or freeze them, impacting availability for users and potentially causing cascading failures in distributed systems.