OpenSSL CMS AuthEnvelopedData Processing May Accept Forged Messages
CVE-2026-34182 is a flaw in OpenSSL's Cryptographic Message Syntax (CMS) handling for AuthEnvelopedData containers. The vulnerable code fails to sufficiently validate attacker-controlled cipher selection and authentication tag length fields during CMS_decrypt() processing. Two abuse paths are described in the provided content. First, OpenSSL may accept an AuthEnvelopedData object that specifies a non-AEAD cipher where an authenticated cipher is expected; an attacker can replay a legitimate recipientInfos structure so the victim unwraps the genuine content-encryption key (CEK), while rewriting the inner algorithm identifier to AES-256-OFB and supplying attacker-chosen IV and ciphertext. In that case OpenSSL decrypts under the real CEK, does not meaningfully enforce the MAC for the modified message, and returns success. Second, OpenSSL accepts an attacker-reduced AEAD tag length, including a one-byte tag, instead of enforcing the expected minimum/range for the selected algorithm. This allows brute-force forgery of the integrity check for CMS content. The issue affects OpenSSL 4.0.0 before 4.0.1, 3.6.0 before 3.6.3, 3.5.0 before 3.5.7, 3.4.0 before 3.4.6, and 3.0.0 before 3.0.21. The provided content states the FIPS modules are not affected.
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An OpenSSL vulnerability addressed in Alpine Linux 3.22.5 and 3.23.5 as part of the June 9, 2026 OpenSSL advisory.
A CMS/PKCS#7 parsing flaw in OpenSSL that allows attacker-controlled AES-GCM authentication tag length reduction, potentially down to one byte, enabling message forgery by brute force.
An OpenSSL vulnerability addressed in Alpine Linux 3.24.1 as part of the June 9, 2026 advisory.
A moderate-severity OpenSSL Cryptographic Message Services validation flaw that can enable integrity check bypass and a timing-oracle style attack leading to key recovery.
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Every observed campaign linking this CVE to a named adversary.
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Cross-references every affected SKU, including bundled OEM variants.
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