OpenSSL Improper Validation of Integrity Check Value Vulnerability - CVE-2026-34181

Issue Summary: The PKCS12 file processing fails to perform sufficient input validation for files that use Password-Based Message Authentication Code 1 (PBMAC1) integrity mechanism allowing a certificate and private key forgery. Impact Summary: An attacker impersonating a user can cause a service reading PKCS12 files to accept forged certificates and private keys with a 1 in 256 probability. If a service accepting PKCS12 files is using passwords for authenticating the received files the attacker can create unencrypted PKCS12 files that use PBMAC1 authentication that specifies an HMAC key of only one byte allowing them to craft a file that will be accepted with a 1 in 256 probability. That would then cause the service to accept a certificate and private key controlled by the attacker. The FIPS modules are not affected by this issue as the affected code is outside the OpenSSL FIPS module boundary.