CVE-2026-63072

About vulnerability

Issue summary: OpenSSL CMS decryption sizes the key-unwrap output buffer based on querying the unwrapped key size, but the AES-WRAP-PAD unwrap primitive can write and cleanse more bytes than that query reports, causing an 8-byte out-of-bounds heap write.

Impact summary: An attacker who supplies a crafted CMS message can trigger a deterministic 8-byte out-of-bounds heap write when the victim decrypts it with CMS_decrypt(), corrupting the heap and typically resulting in a Denial of Service.

CWE: CWE-787: Out-of-bounds Write

Description: The key-wrap OID is potentially attacker-controlled on the wire. CMS unwrapping allows both id-aesNNN-wrap-pad and id-aesNNN-wrap ciphers. An attacker can take a legitimate message and change a single OID byte to select the padded variant while leaving the message otherwise valid. Since the unwrap key is derived from the recipient’s private operation (ECDH key agreement or ML-KEM decapsulation), the RFC 5649 integrity check cannot pass, and the decryption fails with integrity failure.

The write is a fixed-size (8-byte), fixed-value (zero) heap overflow immediately past the allocation, requires no special configuration, and is reachable from the public CMS_decrypt() function. The consequence is a heap corruption leading to a Denial of Service. The fix in the CMS code sizes the unwrap output buffer for the worst case so a failed unwrap cannot write past the allocation.

FIPS impact: no

As the CMS code lives outside the FIPS module boundary, no FIPS modules are affected by this CVE.

Affected product:

AlmaLinux 9.2 ESU , Alpine Linux 3.23 , Alpine Linux 3.24 , Amazon Linux 2 ELS , CentOS 7 ELS , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , CloudLinux 7 ELS , Debian 10 , Debian 10 ELS , Debian 11 , Debian 11 ELS , Debian 12 , Debian 13 , EL 10 , EL 7 , EL 8 , EL 9 , Oracle Linux 7 ELS , RHEL 7 ELS , TuxCare 9.6 ESU , TuxCare 9.8 ESU , Ubuntu 16.04 , Ubuntu 16.04 ELS , Ubuntu 18.04 , Ubuntu 18.04 ELS , Ubuntu 20.04 , Ubuntu 20.04 ELS , Ubuntu 22.04 , Ubuntu 24.04 , Ubuntu 26.04

Affected packages:

openssl @ 1.1.1f (+38 more)