CVE-2026-22796 in OpenSSL
Summary
by MITRE • 01/27/2026
Issue summary: A type confusion vulnerability exists in the signature verification of signed PKCS#7 data where an ASN1_TYPE union member is accessed without first validating the type, causing an invalid or NULL pointer dereference when processing malformed PKCS#7 data.
Impact summary: An application performing signature verification of PKCS#7 data or calling directly the PKCS7_digest_from_attributes() function can be caused to dereference an invalid or NULL pointer when reading, resulting in a Denial of Service.
The function PKCS7_digest_from_attributes() accesses the message digest attribute value without validating its type. When the type is not V_ASN1_OCTET_STRING, this results in accessing invalid memory through the ASN1_TYPE union, causing a crash.
Exploiting this vulnerability requires an attacker to provide a malformed signed PKCS#7 to an application that verifies it. The impact of the exploit is just a Denial of Service, the PKCS7 API is legacy and applications should be using the CMS API instead. For these reasons the issue was assessed as Low severity.
The FIPS modules in 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the PKCS#7 parsing implementation is outside the OpenSSL FIPS module boundary.
OpenSSL 3.6, 3.5, 3.4, 3.3, 3.0, 1.1.1 and 1.0.2 are vulnerable to this issue.
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Analysis
by VulDB Data Team • 03/13/2026
This vulnerability represents a type confusion issue within OpenSSL's PKCS#7 signature verification implementation that stems from inadequate validation of ASN1_TYPE union members during processing of malformed data. The flaw exists specifically in the PKCS7_digest_from_attributes() function where the code accesses the message digest attribute value without first confirming the type of the ASN1_TYPE union member. When the expected V_ASN1_OCTET_STRING type is not present, the code attempts to access invalid memory through the union, leading to pointer dereference errors that ultimately result in application crashes. This type of vulnerability falls under CWE-466, which specifically addresses the use of an incorrect type in memory access operations, and demonstrates how improper union type validation can lead to memory corruption scenarios.
The operational impact of this vulnerability manifests as a denial of service condition where applications that process PKCS#7 signed data become unresponsive or crash when encountering malformed input. The attack vector requires an external party to provide specially crafted PKCS#7 data to a vulnerable application, making this a remote exploitation scenario. While the vulnerability is classified as low severity due to its limited impact scope, the underlying issue represents a fundamental flaw in input validation that could potentially be leveraged in more sophisticated attacks if combined with other vulnerabilities. The fact that this affects legacy PKCS#7 APIs rather than the newer CMS APIs indicates a design flaw in how older cryptographic interfaces handle type validation, which aligns with ATT&CK technique T1203 for process injection and T1499 for endpoint denial of service.
The vulnerability affects multiple OpenSSL versions including 3.6, 3.5, 3.4, 3.3, 3.0, 1.1.1, and 1.0.2, indicating this is a long-standing issue that has persisted across major releases. Notably, the FIPS modules in versions 3.5, 3.4, 3.3, and 3.0 remain unaffected because the PKCS#7 parsing implementation resides outside the FIPS module boundary, demonstrating how modular architecture decisions can provide security isolation. This vulnerability highlights the importance of proper type validation in cryptographic libraries, as the lack of validation in ASN1_TYPE union access creates a direct path to memory corruption. Organizations using vulnerable OpenSSL versions should prioritize upgrading to patched releases, particularly given that PKCS#7 APIs are considered legacy and applications should migrate to CMS APIs for better security posture and future compatibility. The vulnerability serves as a reminder of the critical need for robust input validation in cryptographic implementations and the potential for seemingly benign type confusion issues to result in complete system availability compromise.