CVE-2026-71892— RFC 9709 HKDF派生密钥未执行CMS密钥传输接收方密钥大小验证
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 之前的版本中，针对 CMS 密钥传输接收方（ ）的可选密钥长度验证功能，在使用 RFC 9709 内容加密密钥派生（ ）的消息上从未执行。原本应选择在密钥派生 参数中携带的实际内容加密算法的代码分支，将加密密钥的字节数组与 对象标识符（OID）进行了比较。由于这是对字节数组与 之间的比较，其结果始终为 false，因此该检查最终回退到对外层包装 OID 的密钥长度查找。该 OID 标识的是密钥派生构造而非密码算法，且没有注册密钥长度，因此整个密钥长度比较被
可能的 ATT&CK 技术 1 AI
T1190 · Exploit Public-Facing Application
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一、 漏洞 CVE-2026-71892 基础信息
漏洞信息
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Vulnerability Title
CMS key-transport recipient key-size validation never runs for RFC 9709 HKDF-derived keys
来源: CVE Program / CVE List V5
Vulnerability Description
In Bouncy Castle for Java before 1.86, the opt-in key-size validation on CMS key-transport recipients, org.bouncycastle.cms.jcajce.JceKeyTransRecipient.setKeySizeValidation(true), never ran for a message using RFC 9709 content-encryption key derivation (id-alg-cek-hkdf-sha256). The branch that should have selected the actual content-encryption algorithm carried in the key derivation AlgorithmIdentifier's parameters compared the encrypted-key byte array against the id-alg-cek-hkdf-sha256 object identifier, a comparison between a byte array and an ASN1ObjectIdentifier that is false for every possible input, so the check fell through to a key-size lookup on the outer wrapper OID. That OID identifies a key-derivation construction rather than a cipher and has no registered key size, so the size comparison was skipped entirely. A key-transport EnvelopedData or AuthEnvelopedData whose transported, HKDF-derived content-encryption key did not match the key size of the advertised content-encryption algorithm was therefore accepted even with validation explicitly enabled, silently defeating the only mechanism the API offers for enforcing recovered key size. The recipient now dispatches on the content-encryption AlgorithmIdentifier's algorithm OID, so validation checks the recovered key against the inner content-encryption algorithm. Messages with a matching key size, non-HKDF messages, and recipients that do not enable validation are unaffected. This issue also affects Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 2.0.13 (2.0.X series) and 2.1.13 (2.1.X series).
来源: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/U:Amber
来源: CVE Program / CVE List V5
Vulnerability Type
不充分的比较
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 | 1.78 ~ 1.86 | - |
|
| Legion of the Bouncy Castle Inc. | BC-FJA | 2.0.7 ~ 2.0.13 | - |
|
二、漏洞 CVE-2026-71892 的公开POC
| # | POC 描述 | 源链接 | 神龙链接 |
|---|
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CVE-2026-71892 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-2026-71890 | 8.7 HIGH | MLS外部提交可移除任意组成员漏洞 |
| 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-2026-18040 | 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-2026-71892
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