AIKIDO-2026-879835

bctls-jdk15on is vulnerable to Denial of Service (DoS)

Denial of Service (DoS)CVE-2026-59646 Published Aug 5, 2026

Medium Risk

This Affects:

bctls-jdk15on

1.57 - 1.70

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TL;DR

The DTLS handshake reassembler sizes each reassembly buffer from the full-message length declared in a handshake fragment header, a 24-bit value up to about 16 MiB, without bounding it against the peer's configured maximum handshake message size. Reassemblers are created per message sequence across the receive-ahead window at epoch zero, before any signature or Finished verification. A few small datagrams carrying minimal fragments with large declared lengths therefore commit large amounts of heap per peer, causing a pre-authentication denial of service. The fix bounds the reassembly allocation by the peer's maximum handshake message size before allocating.

Who does this affect?

You are affected if you are using a version that falls within the vulnerable range and you use the Bouncy Castle DTLS client or server to process handshakes from untrusted network peers.

Background info

bctls-jdk15on is vulnerable to Denial of Service (DoS) in versions 1.57 - 1.70.

How to fix this

Migrate the org.bouncycastle:bctls-jdk15on dependency to org.bouncycastle:bctls-jdk18on 1.85 or later, or to org.bouncycastle:bctls-jdk15to18 1.85 or later if you cannot move to Java 8, as the jdk15on coordinates receive no security fixes.