Critical Heap Use-After-Free RCE in OpenSSL PKCS7_verify - CVE-2026-45447

Cryptographic message forgery in OpenSSL (branches 3.0.x, 3.4.x, 3.5.x, 3.6.x, and 4.0.0) allows an attacker to craft CMS AuthEnvelopedData messages that pass authentication and are accepted as genuine, defeating the integrity guarantee of CMS authenticated encryption. Any application relying on OpenSSL's CMS layer to reject tampered or forged authenticated-envelope messages can be tricked into processing attacker-controlled content as trusted. There is no public exploit identified at time of analysis, EPSS is 0.00%, and CISA SSVC lists exploitation status as none, but the flaw is network-reachable with no privileges required.

Heap buffer overflow in OpenSSL's ASN.1 multibyte string conversion routine allows remote attackers to corrupt memory and potentially achieve code execution against applications using affected OpenSSL versions prior to 4.0.1. The flaw was disclosed via the OpenSSL 4.0.1 security patch release alongside 17 other CVEs and is classified as a high-severity issue (CVSS 8.1) with no public exploit identified at time of analysis.

Denial of service in OpenSSL 3.6.0-3.6.2 and 4.0.0 allows remote attackers to crash applications by triggering a NULL pointer dereference during certificate verification when OCSP checking is enabled. The flaw is patched in OpenSSL 4.0.1 (and 3.6.3) per the vendor's 2026-06-09 security advisory; no public exploit identified at time of analysis, and the issue is not listed in CISA KEV.

Denial of service in OpenSSL QUIC implementation allows remote unauthenticated attackers to exhaust server memory by sending crafted PATH_CHALLENGE frames that trigger unbounded memory growth in the QUIC handler. The flaw affects OpenSSL branches 3.4.x, 3.5.x, 3.6.x, and 4.0.0, and is fixed in the 4.0.1 security release alongside numerous other CVEs. No public exploit identified at time of analysis and EPSS is very low (0.02%), but the network-reachable, no-auth nature of QUIC server endpoints makes the issue operationally relevant for TLS/QUIC-facing services.

Denial-of-service in OpenSSL's ASN.1 content parser allows remote unauthenticated attackers to trigger a heap buffer over-read that can crash applications relying on the library for cryptographic parsing. Disclosed via the OpenSSL 4.0.1 security release on 2026-06-09 alongside more than a dozen other fixes, this issue affects every supported branch from 1.0.2 through 3.6 and 4.0. No public exploit identified at time of analysis and the flaw is not listed in CISA KEV, but the broad install base of OpenSSL across servers, clients, and embedded devices makes patching a priority.

Confidentiality break in OpenSSL's AES-OCB implementation stems from the EVP_Cipher() code path ignoring the caller-supplied initialization vector (IV), causing the cipher to operate with a fixed/default IV instead. Affected branches include 3.0.x prior to 3.0.21, 3.4.x prior to 3.4.6, 3.5.x prior to 3.5.7, 3.6.x prior to 3.6.3, and 4.0.0, fixed in OpenSSL 4.0.1 and corresponding maintenance releases. With no public exploit identified at time of analysis and no CISA KEV listing, the issue is rated High (CVSS 7.5) due to high confidentiality impact via network-reachable cryptographic operations.

Denial of service in OpenSSL 3.5.x, 3.6.x, and 4.0.0 stems from a NULL pointer dereference triggered during QUIC server initial packet handling, allowing remote unauthenticated attackers to crash affected servers by sending crafted QUIC traffic. The flaw was disclosed via the OpenSSL 4.0.1 security release on 2026-06-09 alongside multiple other CVEs; no public exploit identified at time of analysis and no CISA KEV listing. Patched versions are available from the upstream project and downstream distributions including Ubuntu (USN-8414-1).

Out-of-bounds read in OpenSSL's CMS password-based decryption code (CVE-2026-9076) allows remote attackers to cause denial of service against applications that decrypt attacker-supplied CMS messages. The flaw is fixed in OpenSSL 4.0.1 alongside a batch of other cryptographic vulnerabilities, with no public exploit identified at time of analysis and no CISA KEV listing. Multiple OpenSSL branches (1.0.2, 1.1.1, 3.0, 3.4, 3.5, 3.6, and 4.0.0) require updates per the upstream advisory.