CVE-2026-63072
Received Received - Intake

OpenSSL CMS Decryption Heap Out-of-Bounds Write

Publication date: 2026-08-25

Last updated on: 2026-08-25

Assigner: OpenSSL Software Foundation

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.

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Meta Information

Published
2026-08-25
Last Modified
2026-08-25
Generated
2026-08-25
AI Q&A
2026-08-25
EPSS Evaluated
N/A
NVD
CVE-2026-63072
EUVD
EUVD-2026-65482

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
openssl openssl to 2026-63072 (inc)

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-787 The product writes data past the end, or before the beginning, of the intended buffer.

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Executive Summary

This vulnerability is an out-of-bounds write in OpenSSL's CMS decryption process. When decrypting a crafted CMS message, the system incorrectly calculates the buffer size for key unwrapping, leading to an 8-byte heap write beyond the allocated memory. This corrupts the heap and typically causes a Denial of Service.

Detection Guidance

This vulnerability can be detected by checking the OpenSSL version in use. If your system uses OpenSSL 3.0.0 through 3.0.16 or 3.1.0 through 3.1.8, it is vulnerable. Run 'openssl version' to check the installed version.

Impact Analysis

An attacker can exploit this by sending a specially crafted CMS message. If you decrypt it using CMS_decrypt(), the heap corruption will likely crash your application, resulting in a Denial of Service. No special configuration is needed for exploitation.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR or HIPAA as it is a technical flaw in OpenSSL's AES-WRAP-PAD unwrap functionality. The issue causes a heap corruption leading to Denial of Service but does not involve data breaches or unauthorized access to sensitive information.

Mitigation Strategies

Immediately update OpenSSL to version 3.0.17 or later for the 3.0.x branch, or 3.1.9 or later for the 3.1.x branch. If updating is not possible, disable CMS decryption functionality or restrict access to the CMS_decrypt() function until the update is applied.

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