CVE-2026-71890— MLS外部提交可移除任意组成员漏洞
一分钟漏洞结论
影响对象
Legion of the Bouncy Castle Inc. BC-JAVA
利用判断
尚无明确在野利用证据，仍需结合暴露面评估
建议动作
优先检查厂商安全公告和参考链接中的修复版本；无法立即升级时，限制受影响服务暴露并加强监测。
在 Bouncy Castle for Java 1.86 版本之前，对 MLS（RFC 9420）外部加入（external commit）中提案列表的验证存在缺陷。具体而言， 方法仅按类型统计提案数量并对已移除叶节点索引进行边界检查，但从未验证该被移除的叶节点是否与加入者（joiner）相关。 根据 RFC 9420 第 12.2 节的规定，外部加入（external commit）中最多允许包含一个“移除”（Remove）提案，该提案用于加入者移除其自身的一个旧版本身份；并且当存在此类移除提案时，commit
可能的 ATT&CK 技术 1 AI
T1190 · Exploit Public-Facing Application
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一、 漏洞 CVE-2026-71890 基础信息
漏洞信息
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Vulnerability Title
MLS external commit can remove an arbitrary group member
来源: CVE Program / CVE List V5
Vulnerability Description
In Bouncy Castle for Java before 1.86, validation of an MLS (RFC 9420) external commit's proposal list, org.bouncycastle.mls.protocol.Group.validateExternalCachedProposals, counted the proposals by type and bounded the removed leaf index but never established that the removed leaf had anything to do with the joiner. RFC 9420 sec. 12.2 permits at most one Remove proposal in an external commit, with which the joiner removes an old version of themselves, and requires that where one is present the LeafNode in the commit's path field meet the criteria it would have to meet in an Update for the removed leaf, in particular that its credential present identifiers acceptable for the removed participant. The ordinary proposal-list validator's self-remove rule is deliberately not applied on this path, because a resync commit legitimately removes a leaf the joiner owns, but nothing was put in its place. Any party holding the group's public GroupInfo, which is precisely what an external joiner is meant to be given, could therefore commit a Remove naming any member's LeafIndex and have every member apply it, evicting that member and taking over their slot in the ratchet tree. The credential check that should have prevented this existed only in the gRPC interop harness and so protected no other caller of the public Group.externalJoin and Group.handle API. An external commit carrying a Remove is now accepted only when the removed leaf's credential is identical to the one in the joiner's own new leaf, on both the sending and the receiving side.
来源: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/U:Amber
来源: CVE Program / CVE List V5
Vulnerability Type
授权机制不正确
来源: CVE Program / CVE List V5
受影响产品
| 厂商 | 产品 | 影响版本 | CPE | 订阅 |
|---|---|---|---|---|
| Legion of the Bouncy Castle Inc. | BC-JAVA | 1.73 ~ 1.86 | - |
|
二、漏洞 CVE-2026-71890 的公开POC
| # | POC 描述 | 源链接 | 神龙链接 |
|---|
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CVE-2026-71890 其他参考 (2)
同批安全公告 · Legion of the Bouncy Castle Inc. · 2026-10-03 · 共 12 条
| CVE-2026-71885 | 9.2 CRITICAL | MLS X.509凭证未绑定到LeafNode签名密钥 |
| CVE-2026-71888 | 8.7 HIGH | CMS 认证数据暴露攻击者插入的authAttrs |
| CVE-2026-71889 | 8.7 HIGH | PKIXCertPathReviewer X.509名称约束绕过漏洞 |
| CVE-2026-85515 | 8.2 HIGH | OpenPGP消息截断未报告，绕过SEIPDv1完整性检查 |
| CVE-2026-71887 | 8.2 HIGH | OpenPGP 签名子键无交叉认证漏洞 |
| CVE-2026-71883 | 8.2 HIGH | Native AES密文解析器泄露原始AES密钥 |
| CVE-2026-71886 | 8.2 HIGH | OpenPGP 子键无证书认证漏洞 |
| CVE-2026-71891 | 7.1 HIGH | BLS12-381 密钥验证接受基于外部曲线的公钥 |
| CVE-2026-71892 | 6.9 MEDIUM | RFC 9709 HKDF派生密钥未执行CMS密钥传输接收方密钥大小验证 |
| CVE-2026-18040 | 5.9 MEDIUM | HQC 通过秘密索引表和采样器泄露私钥信息 |
| CVE-2026-97873 | 5.3 MEDIUM | JCA原始提供程序未限制PBES1和PKCS#12迭代次数 |
IV. Related Vulnerabilities
V. Comments for CVE-2026-71890
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