The vulnerability lies in the OpenPGP Argon2 S2K implementation in Bouncy Castle for Java, where the algorithm honours attacker‑chosen memory and passes values. This allows a malicious user to craft messages that require arbitrarily large amounts of memory to decrypt, potentially exhausting system resources. The flaw is classified as CWE‑770 and carries a CVSS score of 6.9, indicating a moderate severity based on memory consumption and availability impact.

The affected products are the Bouncy Castle for Java libraries, including the standard Java code, the LTS distribution, and the FIPS‑compliant BC‑FJA build. Versions prior to 1.85 for the standard library, before 2.73.12 for the LTS library, and for the FIPS build prior to bcpg‑fips 1.0.13 (1.0.X series), 2.0.13 (2.0.X series), and 2.1.13 (2.1.X series) are vulnerable. All three product lines are maintained by the Legion of the Bouncy Castle Inc.

The exploit requires the ability to supply a crafted OpenPGP message to the vulnerable library. Although the CVE does not provide explicit evidence of remote exploitation, the nature of the flaw suggests that a remote attacker who can inject data into the application could cause high memory usage, leading to denial of service. The EPSS score is < 1%, and the vulnerability is not currently listed in the CISA KEV catalog. The moderate CVSS score indicates a realistic threat, but no public exploits are reported.