Bouncy Castle Java EUVD-2026-52025

The vulnerability fires during OpenPGP certificate parsing in UserAttributeSubpacketInputStream-it is pre-authentication by nature, requiring no credentials or session. No special server configuration or non-default feature flag is required; any application that passes attacker-controlled data to Bouncy Castle's OpenPGP parsing path is vulnerable. The primary real-world prerequisite is that the application exposes an OpenPGP certificate import or processing path reachable from untrusted network input (e.g., a PGP key server lookup, public certificate upload endpoint, or externally submitted signed message handler). Applications that exclusively parse OpenPGP certificates from fully controlled, internal, or trusted-pipeline sources face negligible real-world risk despite the theoretical network vector. Exploitation is limited to availability impact only-no authentication bypass, no data access. The CVSS 4.0 vector (PR:N/UI:N/AV:N/AC:L) confirms no privileges, user interaction, or special attack prerequisites are needed.

The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VA:H) confirms a remotely exploitable, unauthenticated, low-complexity denial-of-service with high availability impact and no attack requirements. The attack is trivially automatable: a single malformed certificate triggers allocation exhaustion before any authentication check can occur. No EPSS data was provided in the source intelligence; the absence of a KEV listing suggests no confirmed widespread active exploitation at time of analysis. However, Bouncy Castle is one of the most pervasive cryptographic libraries in the Java ecosystem, meaning the downstream exposure surface across application servers, key management services, and PGP-enabled mail infrastructure is very broad. The availability-only impact (VC:N/VI:N/VA:H) means no data exfiltration or tampering is possible, but a successful attack causes JVM heap exhaustion leading to OutOfMemoryError or process termination in any service parsing untrusted OpenPGP certificates. The 'Information Disclosure' tag in the CVE record is inconsistent with the technical impact described in the advisory and commit diff, which show a pure DoS; this tag should not be treated as confirmed. The fix is available and straightforward to apply, keeping remediation cost low.

An attacker constructs a malicious OpenPGP certificate containing a User Attribute subpacket with a 4-octet length header declaring approximately 2 GiB of body data, then submits it to any service endpoint-such as a PGP key import API, key server query handler, or signed-message verification service-backed by a vulnerable Bouncy Castle version. The JVM allocates a multi-gigabyte byte array before reading any body content, triggering an OutOfMemoryError or JVM process termination. No public proof-of-concept has been confirmed at time of analysis, but the attack structure is directly reconstructable from the public commit diff.