CVE-2026-34181 — PKCS#12 Files with PBMAC1 Are Accepted with Short HMAC Keys

Affected: OpenSSL

Issue Summary: The PKCS#12 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 PKCS#12 files to accept forged certificates and private keys with a 1 in 256 probability.

If a service accepting PKCS#12 files is using passwords for authenticating the received files, the attacker can create unencrypted PKCS#12 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.

USN-8414-1 — openssl vulnerabilities

Affected: Ubuntu:22.04:LTS: openssl, Ubuntu:24.04:LTS: openssl, Ubuntu:25.10: openssl, Ubuntu:26.04:LTS: openssl

Frank Buss discovered that OpenSSL had a heap buffer over-read in ASN.1 content parsing. An attacker could possibly use this issue to cause OpenSSL to crash, resulting in a denial of service, or obtain sensitive information. (CVE-2026-34180)

Pavol Zacik and Alex Gaynor discovered that OpenSSL incorrectly accepted PKCS#12 files with short HMAC keys when using PBMAC1. An attacker could possibly use this issue to bypass integrity checks. This issue only affected Ubuntu 25.10 and Ubuntu 26.04 LTS. (CVE-2026-34181)

Asim Viladi Oglu Manizada and Alex Gaynor discovered that OpenSSL could accept forged CMS AuthEnvelopedData messages. An attacker could possibly use this issue to bypass message authentication checks. (CVE-2026-34182)

Abhinav Agarwal discovered that OpenSSL had unbounded memory growth in the QUIC PATH_CHALLENGE handler. A remote attacker could possibly use this issue to cause OpenSSL to use excessive resources, leading to a denial of service. This issue only affected Ubuntu 25.10 and Ubuntu 26.04 LTS. (CVE-2026-34183)

Sunwoo Lee, Hyuk Lim, and Seunghyun Yoon discovered that OpenSSL had a NULL pointer dereference in QUIC server initial packet handling. A remote attacker could possibly use this issue to cause OpenSSL to crash, resulting in a denial of service. This issue only affected Ubuntu 25.10 and Ubuntu 26.04 LTS. (CVE-2026-42764)

Mayank Jangid, Kushal Khemka, Hari Priandana, Bhabani Sankar Das, and Qifan Zhang discovered that OpenSSL had a possible NULL derefe…

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CVE-2026-34181 — PKCS#12 Files with PBMAC1 Are Accepted with Short HMAC Keys

USN-8414-1 — openssl vulnerabilities