Review reviewHigh

CVE-2026-28388

OpenSSL OpenSSL, SIMATIC CN 4100, SIMATIC S7-1500 TM MFP - GNU/Linux subsystem

Issue summary: When a delta CRL that contains a Delta CRL Indicator extension is processed a NULL pointer dereference might happen if the required CRL Number extension is missing. Impact summary: A NULL pointer dereference can trigger a crash which leads to a Denial of Service for an application. When CRL processing and delta CRL processing is enabled during X.509 certificate verification, the delta CRL processing does not check whether the CRL Number extension is NULL before dereferencing it. When a malformed delta CRL file is being processed, this parameter can be NULL, causing a NULL poi...

CVSS: 7.5
EPSS: 1.06%
CISA KEV: Not listed
Published: 2026.04.08

PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability1.06%

Technical severityCVSS 7.5

Vulnerability overview

Affected product and versions

Product: OpenSSL OpenSSL, SIMATIC CN 4100, SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
Affected versions: >= 3.6.0 < 3.6.2, >= 3.5.0 < 3.5.6, >= 3.4.0 < 3.4.5, >= 3.3.0 < 3.3.7, >= 3.0.0 < 3.0.20, >= 1.1.1 < 1.1.1zg, >= 1.0.2 < 1.0.2zp, < V5.0
Fixed versions: 1.0.2zp, 1.1.1zg, 3.0.20, 3.3.7, 3.4.5, 3.5.6, 3.6.2

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that OpenSSL OpenSSL, SIMATIC CN 4100, SIMATIC S7-1500 TM MFP - GNU/Linux subsystem and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
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-476