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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
2026-06-16
Advisory published
2026-06-09
Advisory updated
2026-06-16

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.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-9076 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-9076

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-9076 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-9076

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.