CVE-2026-63072

01/Description

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.

02/Affected products

openssl: openssl

03/References6

• openssl-library.org/news/secadv/20260825.txt Vendor Advisory
• github.com/openssl/openssl/commit/2a3dac874c8057c1f0186849bf1ed… Patch
• github.com/openssl/openssl/commit/87784ad619af36b8807c2044b3940… Patch
• github.com/openssl/openssl/commit/9530a5fd1aacaeccdced4478ea234… Patch
• github.com/openssl/openssl/commit/9ec2f6d2ae2bcad907cf7ee385848… Patch
• github.com/openssl/openssl/commit/a0c8ec557d9cac078f032d76cdf68… Patch