CVE-2026-17507 MLS membership checks compare a uint32 leaf_index as signed, admitting an out-of-range sender

In Bouncy Castle for Java before 1.86, the MLS implementation org.bouncycastle.mls holds RFC 9420's uint32 leafindex in a signed int, so a wire value with the top bit set decodes to a negative number. That is a legitimate encoding rather than malformed input, and it must still decode, since the M...

CVE-2026-17507

The Bouncy Castle for Java library (before version 1.86 ) contains a vulnerability in the MLS implementation (org.bouncycastle.mls). The root cause is a signed to unsigned conversion error where an RFC 9420 uint32 leaf_index is stored as a signed integer. Because values with the top bit set decod...

CVE-2026-17507 MLS membership checks compare a uint32 leaf_index as signed, admitting an out-of-range sender

In Bouncy Castle for Java before 1.86, the MLS implementation org.bouncycastle.mls holds RFC 9420's uint32 leafindex in a signed int, so a wire value with the top bit set decodes to a negative number. That is a legitimate encoding rather than malformed input, and it must still decode, since the M...

EUVD-2026-91235

In Bouncy Castle for Java before 1.86, the MLS implementation org.bouncycastle.mls holds RFC 9420's uint32 leafindex in a signed int, so a wire value with the top bit set decodes to a negative number. That is a legitimate encoding rather than malformed input, and it must still decode, since the M...