How to Fix CVE-2026-28388: OpenSSL (Bundle Sibling)

*By Sai Kiran Pandrala*

Last verified: 2026-05-25

CVE-2026-28388 is a sibling vulnerability in the same Openssl OpenSSL advisory bundle as CVE-2026-28386. The same patched build closes every CVE in the bundle, so the remediation procedure for CVE-2026-28388 matches the primary write-up.

What is different about CVE-2026-28388?

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.

Impact is consistent with the bundle: remote code execution on the affected system. The patched build closes every code path in the advisory in one update.

How to fix CVE-2026-28388

Apply the patched build per the primary write-up: How to Fix CVE-2026-28386.

For a quick check, confirm the running version of OpenSSL:

openssl version

Frequently asked questions

Is CVE-2026-28388 being actively exploited?

Not at the time of writing. It is not listed in CISA's Known Exploited Vulnerabilities catalog. That status can change, so monitor the vendor advisory and the KEV catalog if the system is exposed.

How severe is CVE-2026-28388?

CVSS rates it 7.5 (High). Use that score to set your patch priority alongside the other items in your queue.

Do I have to take OpenSSL offline to apply the patch?

It depends on the deployment. High-availability or clustered installs can usually patch one node at a time with no full outage. Standalone installs typically need a short restart. Always follow the vendor's documented upgrade steps.

What if my vulnerability scanner still flags CVE-2026-28388 after I patch?

Re-run the scan after a service restart, then confirm the scanner's plugin set is up to date. Some scanners detect by banner version only and lag the official fix metadata by a release.

References

• Official vendor advisory: https://openssl-library.org/news/secadv/20260407.txt
• NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2026-28388
• CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
• Primary write-up: How to Fix CVE-2026-28386

*Written by Sai Kiran Pandrala. Last verified 2026-05-25. Part of the Openssl OpenSSL advisory bundle. Full procedure at how-to-fix-cve-2026-28386.*