NULL Pointer Dereference Vulnerability in OpenSSL's Certificate Verification
CVE-2026-28388

7.5HIGH

Key Information:

Vendor

OpenSSL
Status
OpenSSL
Vendor
CVE Published:
7 April 2026

What is CVE-2026-28388?

A vulnerability exists in OpenSSL's handling of delta CRLs during X.509 certificate verification. When processing a delta CRL that lacks the required CRL Number extension, the system may attempt to dereference a NULL pointer. This can lead to application crashes and result in Denial of Service. The issue is primarily relevant when the X509_V_FLAG_USE_DELTAS flag is enabled, and a malformed CRL is supplied. It does not allow for code execution or memory disclosure.

Affected Version(s)

OpenSSL 3.6.0 < 3.6.2

OpenSSL 3.5.0 < 3.5.6

OpenSSL 3.4.0 < 3.4.5

References

https://openssl-library.org/news/secadv/20260407.txt
vendor-advisory
https://github.com/openssl/openssl/commit/602542f2c0c2d5e...
patch
https://github.com/openssl/openssl/commit/d3a901e8d9f021f...
patch

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Igor Morgenstern (Aisle Research)
Igor Morgenstern (Aisle Research)
.