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Mallory
Medium

ASN1_TYPE Type Confusion in OpenSSL PKCS7_digest_from_attributes()

IdentifiersCVE-2026-22796CWE-843

CVE-2026-22796 is a type confusion vulnerability in OpenSSL's legacy PKCS#7 signature verification path, specifically in the PKCS7_digest_from_attributes() function. The function reads the messageDigest attribute from signed PKCS#7 data and accesses an ASN1_TYPE union member without first validating that the attribute type is V_ASN1_OCTET_STRING. When a malformed signed PKCS#7 object supplies an unexpected ASN.1 type, the code dereferences an invalid or NULL pointer through the ASN1_TYPE union, causing a crash during signature verification or when the function is called directly. The issue affects OpenSSL 3.6, 3.5, 3.4, 3.3, 3.0, 1.1.1, and 1.0.2. The OpenSSL FIPS modules in 3.5, 3.4, 3.3, and 3.0 are not affected because the vulnerable PKCS#7 parsing code is outside the FIPS module boundary.

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ANALYST BRIEF

Impact, mitigation & remediation

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Impact

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Successful exploitation causes an invalid or NULL pointer dereference, resulting in process termination and Denial of Service. Based on the provided content, the impact is limited to availability loss; there is no indication that this issue enables code execution, privilege escalation, or data disclosure. OpenSSL assessed the issue as Low severity.

Mitigation

If you can’t patch tonight, do this now.

Avoid invoking the legacy PKCS#7 verification path on untrusted input where possible, and prefer the CMS API instead of PKCS#7 APIs. Until patched versions are deployed, reduce exposure by preventing applications from processing attacker-supplied malformed signed PKCS#7 data, adding input filtering/validation around PKCS#7 handling, and isolating or sandboxing services that must verify externally supplied PKCS#7 objects.

Remediation

Patch, then assume compromise.

Upgrade to a fixed OpenSSL release for the affected branch. The provided content indicates fixes are included in OpenSSL 3.6.1, 3.5.5, 3.4.4, 3.3.6, 3.0.19, 1.1.1ze, and 1.0.2zn. Downstream vendors should apply their corresponding patched packages or firmware updates. Where feasible, applications should migrate away from the legacy PKCS#7 API to the CMS API, as recommended by OpenSSL.
PUBLIC EXPLOITS

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VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

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VendorProductType
FreebsdFreebsdapplication
OpenSSL Software FoundationOpensslapplication

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