CVE-2026-45447: Heap Use-After-Free in the PKCS7_verify() Function

Synopsis

Heap use-after-free in OpenSSL's PKCS7_verify() function affects OpenSSL versions across the 1.0.2, 1.1.1, 3.0, 3.4, and 3.5 branches. The vulnerability is reachable over the network by any low-privilege authenticated user, requiring no victim interaction, and successful exploitation causes process crashes, heap corruption, or remote code execution. Patched-image rebuilds at versions 1.0.2zq, 1.1.1zh, 3.0.21, 3.4.6, and 3.5.7 are available on HarborGuard for environments running an affected version.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The vulnerable PKCS7_verify() code path is exposed over the network, so an attacker must be able to deliver a crafted PKCS#7 or S/MIME message to the target service across a network connection.

• AuthenticationRequired

  The CVSS vector specifies PR:L, meaning any low-privilege account is sufficient; no administrative access is needed to supply a malicious signed message.

• Victim interactionNot required

  Exploitation is fully attacker-driven: no user action such as clicking a link or opening a file is needed for the vulnerable code path to execute.

• Attack complexityDetail

  Attack complexity is low (AC:L), meaning the exploit is reliable and does not depend on race conditions, specific memory layouts, or other hard-to-control environmental factors.

Blast Radius

• An attacker who triggers the use-after-free can crash the affected process, causing a denial of service for any application relying on that OpenSSL instance.
• Heap corruption from the freed BIO region can allow an attacker to overwrite adjacent memory structures, enabling arbitrary data reads including session tokens, private keys, or plaintext message content.
• In application contexts where allocator behavior is favorable to the attacker, the corrupted heap enables remote code execution within the process, giving the attacker full control over the affected workload.
• Applications using the PKCS#7 APIs (not the CMS APIs) for signature verification are affected; any service that processes inbound S/MIME email or PKCS#7 signed payloads falls within scope.