OpenSSL up to 4.0.0 PKCS7_verify digestAlgorithms use after free

Summaryinfo

A vulnerability marked as critical has been reported in OpenSSL up to 3.0.20/3.4.5/3.5.6/3.6.2/4.0.0. This affects the function PKCS7_verify. This manipulation of the argument digestAlgorithms causes use after free. This vulnerability is tracked as CVE-2026-45447. The attack is possible to be carried out remotely. No exploit exists. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability has been found in OpenSSL up to 3.0.20/3.4.5/3.5.6/3.6.2/4.0.0 and classified as critical. Affected by this vulnerability is the function PKCS7_verify. The manipulation of the argument digestAlgorithms with an unknown input leads to a use after free vulnerability. The CWE definition for the vulnerability is CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

Issue summary: A specially crafted PKCS#7 or S/MIME signed message could trigger a use-after-free during PKCS#7 signature verification. Impact summary: A use-after-free may result in process crashes, heap corruption, or potentially remote code execution. When processing a PKCS#7 or S/MIME signed message, if the SignedData digestAlgorithms field is present as an empty ASN.1 SET, OpenSSL may incorrectly free a caller-owned BIO during PKCS7_verify(). A subsequent use of the BIO by the calling application results in a use-after-free condition. In the common case this occurs when the application later calls BIO_free() on the BIO originally passed to PKCS7_verify(). Depending on allocator behavior and application-specific BIO usage patterns, this may result in a crash or other memory corruption. In some application contexts this may potentially be exploitable for remote code execution. Applications that process PKCS#7 or S/MIME signed messages using OpenSSL PKCS#7 APIs may be affected. Applications using the CMS APIs for this processing are not affected. The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.

The advisory is shared at openssl-library.org. This vulnerability is known as CVE-2026-45447 since 05/12/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details are known, but no exploit is available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 06/11/2026).

The vulnerability scanner Nessus provides a plugin with the ID 320333 (Linux Distros Unpatched Vulnerability : CVE-2026-45447), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 1.0.2zq, 1.1.1zh, 3.0.21, 3.4.6, 3.5.7, 3.6.3 or 4.0.1 eliminates this vulnerability. Applying the patch 3aad5eb7af4de4ee0633c30a8541a54d9bbde63c is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (320333). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Network Encryption Software

Name

• OpenSSL

Version

• 3.0.0
• 3.0.1
• 3.0.2
• 3.0.3
• 3.0.4
• 3.0.5
• 3.0.6
• 3.0.7
• 3.0.8
• 3.0.9
• 3.0.10
• 3.0.11
• 3.0.12
• 3.0.13
• 3.0.14
• 3.0.15
• 3.0.16
• 3.0.17
• 3.0.18
• 3.0.19
• 3.0.20
• 3.4.0
• 3.4.1
• 3.4.2
• 3.4.3
• 3.4.4
• 3.4.5
• 3.5.0
• 3.5.1
• 3.5.2
• 3.5.3
• 3.5.4
• 3.5.5
• 3.5.6
• 3.6.0
• 3.6.1
• 3.6.2
• 4.0

License

• open-source

Website

• Product: https://www.openssl.org/

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If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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