CVE-2026-28388: NULL Pointer Dereference When Processing a Delta CRL

High severity · published Apr 7, 2026

CVE-2026-28388

NULL Pointer Dereference When Processing a Delta CRL

7.5

CVSS

0.9%

EPSS

On KEV

Description

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 pointer dereference. Exploiting this issue requires the X509_V_FLAG_USE_DELTAS flag to be enabled in the verification context, the certificate being verified to contain a freshestCRL extension or the base CRL to have the EXFLAG_FRESHEST flag set, and an attacker to provide a malformed CRL to an application that processes it. The vulnerability is limited to Denial of Service and cannot be escalated to achieve code execution or memory disclosure. For that reason the issue was assessed as Low severity according to our Security Policy. The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack vector

Network

Complexity

Low

Privileges

None

User interaction

None

Confidentiality

None

Integrity

None

Availability

High

Scope

Unchanged

Exploitation

Is it being used?

Exploit prediction (EPSS)0.9% · higher than 59% of CVEs

Exploited in the wildNo evidence yet

CISA KEVNot listed

Ransomware campaign useNot known

Affected products

Which versions

OpenSSL · OpenSSL

3.6.0 before 3.6.2; 3.5.0 before 3.5.6; 3.4.0 before 3.4.5; 3.3.0 before 3.3.7; 3.0.0 before 3.0.20; 1.1.1 before 1.1.1zg; +1 more · source: vendor, NVD

SIMATIC CN 4100 · Siemens

before V5.0 · source: CISA

SIMATIC S7-1500 TM MFP - GNU/Linux subsystem · Siemens

0 · source: CISA

In the news

VulnerabilityHigh

Hitachi Energy RTU500 Product

View CSAF Summary Hitachi Energy is aware of vulnerabilities that affect RTU500 product versions listed in this document. These vulnerabilities if exploited can have impact on confidentiality, integrity and availability of the product. Please refer to the Recommended Immediate Actions for information about the mitigation/remediation. The following versions of Hitachi Energy RTU500 Product are affected: RTU500 series CMU Firmware vers:RTU500_series_CMU_Firmware/>=13.5.1|<=13.5.4, vers:RTU500_series_CMU_Firmware/>=13.6.1|<=13.6.3, vers:RTU500_series_CMU_Firmware/>=13.7.1|<=13.7.8, vers:RTU500_series_CMU_Firmware/>=13.8.1|<=13.8.2, vers:RTU500_series_CMU_Firmware/>=12.7.1|<=12.7.7 (CVE-2026-17539, CVE-2026-28388, CVE-2026-6732, CVE-2026-6653, CVE-2026-6276, CVE-2026-9079, CVE-2026-11856, CVE-2026-8927, CVE-2026-8932, CVE-2026-17539, CVE-2026-28388, CVE-2026-6732, CVE-2026-6653, CVE-2026-6276, CVE-2026-9079, CVE-2026-11856, CVE-2026-8927, CVE-2026-8932, CVE-2026-17539, CVE-2026-28388, CVE-2026-6732, CVE-2026-6653, CVE-2026-6276, CVE-2026-9079, CVE-2026-11856, CVE-2026-8927, CVE-2026-8932, CVE-2026-17539, CVE-2026-28388, CVE-2026-6732, CVE-2026-6653, CVE-2026-6276, CVE-2026-9079, CVE-2026-11856, CVE-2026-8927, CVE-2026-8932, CVE-2026-17539, CVE-2026-28388, CVE-2026-6653) CVSS Vendor Equipment v3 8.8 Hitachi Energy RTU500 series CMU Firmware 7 Vulnerabilities NULL Pointer Dereference, ...

CVE-2026-17539 CVE-2026-28388 CVE-2026-6732

Oct 20, 2026·US-CERT ICS Advisories

Affected product

OpenSSL

All OpenSSL CVEs

References

NVD

https://nvd.nist.gov/vuln/detail/CVE-2026-28388

CVE.org

https://www.cve.org/CVERecord?id=CVE-2026-28388

Patch

https://github.com/openssl/openssl/commit/59c3b3158553ab53275bbbccca5cb305d591cf2e