CVE-2026-34182: CMS AuthEnvelopedData Processing May Accept Forged Messages
Vendor fix available · Affected: OpenSSL · Exploitation: possible (1 to 10%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 64% of scored CVEs
DescriptionCVE.org
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.
Affected products1
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- OpenSSL · OpenSSLfrom 4.0.0 before 4.0.1; from 3.6.0 before 3.6.3; from 3.5.0 before 3.5.7; from 3.4.0 before 3.4.6; from 3.0.0 before 3.0.21
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No CyberSIXT article names CVE-2026-34182 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.