In BC-JAVA versions prior to 1.86 and 2.73.13, the legacy PBES1 (PKCS#5 scheme 1) and PKCS#12 password-based encryption (PBE) families accept an iteration count parameter from untrusted input without enforcing upper bounds. The iteration count is parsed from AlgorithmParameters implementations (PKCS12PBE, PBKDF1) and can be narrowed incorrectly beyond the integer range, leading to arbitrary amounts of work during password-based key derivation. This lack of throttling can cause resource exhaustion. The fix introduces validation to reject negative or excessively large iteration counts beyond the limit set by the org.bouncycastle.pbe.max_iteration_count property (default 10,000,000), and prevents narrowing beyond the int range during parameter parsing. This vulnerability also affects the LTS branch before version 2.73.13.

An attacker can supply a crafted iteration count parameter that causes the key derivation process to consume excessive CPU resources, potentially leading to denial of service conditions. The vulnerability does not directly disclose sensitive information or allow privilege escalation but can degrade service availability due to resource exhaustion.

A fix is available in Bouncy Castle for Java versions 1.86 and 2.73.13 and later, which enforce iteration count limits and reject invalid parameters. Users should upgrade to these fixed versions to mitigate the vulnerability. No additional vendor advisory or patch links were provided, so patch status is based on the version information in the description. Until upgraded, users should avoid processing untrusted inputs with legacy PBES1 and PKCS#12 PBE schemes or configure the org.bouncycastle.pbe.max_iteration_count property to a safe lower value if possible.