CVE-2026-17507 Affecting bouncycastle package, versions *


Severity

Recommended
0.0
high
0
10

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Threat Intelligence

EPSS
0.34% (27th percentile)

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  • Snyk IDSNYK-ECHOLATEST-BOUNCYCASTLE-20414100
  • published3 Oct 2026
  • disclosed2 Oct 2026

Introduced: 2 Oct 2026

NewCVE-2026-17507  (opens in a new tab)

How to fix?

There is no fixed version for Echo:latest bouncycastle.

NVD Description

Note: Versions mentioned in the description apply only to the upstream bouncycastle package and not the bouncycastle package as distributed by Echo. See How to fix? for Echo:latest relevant fixed versions and status.

In Bouncy Castle for Java before 1.86, the MLS implementation (org.bouncycastle.mls) holds RFC 9420's uint32 leaf_index 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 MLS interop test vectors round-trip the full range. GroupKeySet.SecretTree.hasLeaf and Group.validateRemove compared the decoded value directly against the tree's leaf count, and a signed comparison treats any negative int as less than a positive bound, so an out-of-range sender passed the membership check. In the hasLeaf case the SenderData of an unprotected PrivateMessage could then drive LeafIndex.directPath through NodeIndex.parent() arithmetic that never reaches the tree root, growing the resulting node list without bound until the JVM exhausted its heap. A single small message from any current group member could therefore deny service to every other member of the group. Both comparisons now interpret the value as unsigned via Integer.toUnsignedLong, rejecting an out-of-range sender however it was encoded; well-formed leaf indices are unaffected.

CVSS Base Scores

version 3.1