Affected: OpenSSL

Issue summary: When CMS password-based decryption (RFC 3211 / PWRI key unwrap) processes attacker-supplied CMS data, an attacker-chosen stream-mode KEK cipher can trigger a heap out-of-bounds read in kek_unwrap_key().

Impact summary: A heap buffer over-read may trigger a crash which leads to Denial of Service for an application if the input buffer ends at a memory page boundary and the following page is unmapped. There is no information disclosure as the over-read bytes are not revealed to the attacker.

The key unwrapping function performs a check-byte test as specified in the RFC that reads 7 bytes from a heap allocation that is based on the wrapped key length from the message. There is a minimum length check based on the block length of the wrapping cipher. However the cipher is selected from an OID carried in the attacker's PWRI keyEncryptionAlgorithm with no requirement that the cipher be a block cipher. When an attacker selects a stream-mode cipher the guard will be ineffective and the allocated buffer containing the unwrapped key can be too small to fit the check-bytes specified in the RFC and a buffer over-read can happen.

Applications calling CMS_decrypt() or CMS_decrypt_set1_password() (equivalently openssl cms -decrypt -pwri_password ...) on untrusted CMS data are vulnerable to this issue. No password knowledge is required: the over-read happens during the unwrap attempt before any authentication succeeds.

The over-read is limited to a few bytes and is not writ…

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…