PatchSiren cyber security CVE debrief

CVE-2026-9076 OpenSSL CVE debrief

A high-severity vulnerability, CVE-2026-9076, was found in OpenSSL, a widely-used cryptographic library. The issue arises from a heap buffer over-read during the decryption of CMS (Cryptographic Message Syntax) data. An attacker can exploit this vulnerability by supplying malicious CMS data, potentially leading to a Denial of Service (DoS) attack. The vulnerability has a CVSS score of 7.5 and is considered high-severity.

Vendor: OpenSSL
Product: Unknown
CVSS: HIGH 7.5
CISA KEV: Not listed in stored evidence
Original CVE published: 2026-06-09
Original CVE updated: 2026-06-10
Advisory published: 2026-06-09
Advisory updated: 2026-06-10

Who should care

Developers and administrators using OpenSSL for CMS decryption are advised to take immediate action. This vulnerability can be exploited without requiring any password knowledge, making it a significant concern for applications that process untrusted CMS data.

Technical summary

The vulnerability is caused by the lack of proper validation of the cipher used in the key unwrapping process. An attacker can select a stream-mode cipher, which can lead to a buffer over-read. This over-read is limited to a few bytes and does not disclose any information to the attacker. However, if the allocation borders unmapped memory, it can trigger a crash, leading to a DoS attack.

Defensive priority

High

Recommended defensive actions

Update OpenSSL to the latest version that includes the security patch.
Review and update applications that use OpenSSL for CMS decryption to ensure they are not vulnerable.
Implement additional security measures, such as input validation and error handling, to mitigate the risk of exploitation.

Evidence notes

The vulnerability was reported by OpenSSL and has been assigned CVE-2026-9076. The CVSS score is 7.5, indicating a high-severity vulnerability.

Official resources

CVE-2026-9076 was published on 2026-06-09T17:17:50.997Z and modified on 2026-06-10T08:16:26.063Z.