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CVE-2026-5500 is a flaw in wolfSSL's PKCS7/CMS AuthEnvelopedData parsing, specifically in wc_PKCS7_DecodeAuthEnvelopedData(). The function does not properly sanitize the AES-GCM authentication tag length taken from the received message and does not enforce a lower bound on the tag size. According to the provided content, wolfSSL ignores aes-ICVlen and instead derives the effective tag length from the length of the outer mac field. As a result, a malicious intermediary can re-encode the mac OCTET STRING so that the receiver verifies only a 1-byte GCM tag instead of the normal 16-byte tag. This breaks the intended integrity guarantees of AES-GCM in CMS/PKCS7 AuthEnvelopedData and enables practical forgery attempts by drastically weakening authentication strength.
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A CMS/PKCS#7 parsing flaw in wolfSSL that derives AES-GCM tag length from the attacker-controlled MAC field length, allowing authentication tag truncation to one byte and enabling forgery attempts.
A high-severity cryptographic flaw in wolfSSL allowing CMS AuthEnvelopedData AEAD forgery via GCM tag truncation issues.
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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.
Community discussion across Reddit, Mastodon, and other social sources.