NULL pointer dereference in OpenSSL - CVE-2026-28388
Published: April 9, 2026
Vulnerability identifier: #VU125565
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-28388
CWE-ID: CWE-476
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: OpenSSL Software Foundation
Affected software:
OpenSSL
OpenSSL
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to NULL pointer dereference in delta CRL processing during X.509 certificate verification when processing a malformed delta CRL that contains a Delta CRL Indicator extension but lacks a CRL Number extension. A remote attacker can provide a malformed CRL to cause a denial of service.
Exploitation requires delta CRL processing to be enabled in the verification context and the certificate or base CRL to indicate freshest CRL processing.
How to mitigate CVE-2026-28388
Install security update from vendor's website.