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Review reviewHigh

CVE-2026-9076

OpenSSL OpenSSL, openssl

Issue summary: When CMS password-based decryption (RFC 3211 / PWRI key unwrap) processes attacker-supplied CMS data, an attacker-chosen stream-mode KEK cipher can trigger a heap out-of-bounds read in kek_unwrap_key(). Impact summary: A heap buffer over-read may trigger a crash which leads to Denial of Service for an application if the input buffer ends at a memory page boundary and the following page is unmapped. There is no information disclosure as the over-read bytes are not revealed to the attacker. The key unwrapping function performs a check-byte test as specified in the RFC that read...

CVSS
7.5
EPSS
-
- percentile
CISA KEV
Not listed
Published
2026.06.10
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability-
Technical severityCVSS 7.5

Vulnerability overview

Issue summary: When CMS password-based decryption (RFC 3211 / PWRI key unwrap) processes attacker-supplied CMS data, an attacker-chosen stream-mode KEK cipher can trigger a heap out-of-bounds read in kek_unwrap_key(). Impact summary: A heap buffer over-read may trigger a crash which leads to Denial of Service for an application if the input buffer ends at a memory page boundary and the following page is unmapped. There is no information disclosure as the over-read bytes are not revealed to the attacker. The key unwrapping function performs a check-byte test as specified in the RFC that read...

Affected product and versions

Product
OpenSSL OpenSSL, openssl
Affected versions
>= 4.0.0 < 4.0.1, >= 3.6.0 < 3.6.3, >= 3.5.0 < 3.5.7, >= 3.4.0 < 3.4.6, >= 3.0.0 < 3.0.21, >= 1.1.1 < 1.1.1zh, >= 1.0.2 < 1.0.2zq, 4.0.0
Fixed versions
1.0.2zq, 1.1.1zh, 3.0.21, 3.4.6, 3.5.7, 3.6.3

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that OpenSSL OpenSSL, openssl and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE
CWE-125
CVE-2026-9076 — OpenSSL OpenSSL, openssl | SECUFOCUS NOW