CVE-2026-34182— CMS AuthEnvelopedData Processing May Accept Forged Messages

CMS AuthEnvelopedData Processing May Accept Forged Messages

Issue Summary: Cryptographic Message Services (CMS) processing fails to perform sufficient input validation on the cipher and tag length fields of AuthEnvelopedData containers, leading to various potential compromises. Impact Summary: Attackers making use of these vulnerabilities may achieve key-equivalent functionality for a given CMS recipient and/or bypass integrity validation for a given message. In one use case, an attacker may send a CMS message containing AuthEnvelopedData with the cipher specified as a non-AEAD cipher. OpenSSL erroneously allows this selection, and attempts to decrypt and validate the message. An on-path attacker who captures one legitimate AES-GCM AuthEnvelopedData addressed to the victim can re-emit it with the recipientInfos set left byte-for-byte intact, so the victim's private key still unwraps the genuine CEK (the content-encryption key), but with the inner OID rewritten to AES-256-OFB (Output Feedback Mode, an unauthenticated keystream mode) and with an attacker-chosen IV and ciphertext. The victim initializes AES-256-OFB under the real CEK, never consults the MAC field, and CMS_decrypt() returns success. If the application under attack responds to the attacker with any indicator showing success or failure of the decryption effort, it is possible for the attacker to use this as an oracle to obtain key equivalent functionality for the CEK used for the chosen recipient of the message. In another use case, an attacker can reduce the tag length of the chosen AEAD cipher for a given AuthEnvelopedData container to be a single byte long, allowing an attacker to brute force CMS decryption, producing an integrity bypass for applications that trust CMS_decrypt() to reject modified content. The FIPS modules are not affected by this issue.

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完整性检查值验证不恰当

OpenSSL 安全漏洞

OpenSSL是OpenSSL团队的一个开源的能够实现安全套接层（SSLv2/v3）和安全传输层（TLSv1）协议的通用加密库。该产品支持多种加密算法，包括对称密码、哈希算法、安全散列算法等。 OpenSSL存在安全漏洞，该漏洞源于CMS处理对AuthEnvelopedData中密码和标签长度字段输入验证不足，可能导致攻击者实现密钥等效功能或绕过完整性验证。

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