Incorrect Authorization Affecting org.bouncycastle:bcmls-jdk18on package, versions [1.73,1.86)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published4 Oct 2026
- disclosed3 Oct 2026
- creditYu Bao
Introduced: 3 Oct 2026
NewCVE-2026-71890 (opens in a new tab)How to fix?
Upgrade org.bouncycastle:bcmls-jdk18on to version 1.86 or higher.
Overview
Affected versions of this package are vulnerable to Incorrect Authorization in org.bouncycastle.mls.protocol.Group.validateExternalCachedProposals through external MLS commit Remove proposal validation. An attacker can evict an arbitrary group member and take over that slot in the ratchet tree by supplying an external commit that names that member’s LeafIndex while holding only the group’s public GroupInfo. The vulnerable validation counted Remove proposals and bounded the removed leaf index, but it did not verify that the removed leaf was the joiner’s own prior leaf. As a result, any external joiner could submit a Remove for another participant and have other members apply it, forcing that member out of the group and disrupting the user’s session state.