CVE-2026-28388: Issue summary: When a delta CRL that contains a Delta CRL Indicator extension is processed a NULL pointer dere

Q: How do I fix CVE-2026-28388?

openssl: upgrade to 1.0.2zp, 1.1.1zg, 3.0.20, 3.3.7, 3.4.5, 3.5.6, 3.6.2. Exact commands for each OS are on this page.

Q: Is CVE-2026-28388 being exploited?

CVE-2026-28388 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-28388 affect?

CVE-2026-28388 affects openssl. Severity is high (CVSS 7.5). 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 cr

Q: How urgent is CVE-2026-28388?

Priority 51/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

This month

HIGH 7.5REMOTEWATCHLISTUPGRADE

CVE-2026-28388 is a high-severity flaw (CVSS 7.5) affecting openssl. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.9% (top 41%)
CISA exploited list	No
Weakness	CWE-476
Published	2026-04-07
Last modified	2026-07-24

Publisher (CNA): OpenSSL Software Foundation · Vendor: openssl

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-07 22:16 UTCPublished CVE record published
2026-07-24 23:10 UTCUpdated Record last modified

openssl openssl UPGRADE

Affected: >= 1.0.2 and < 1.0.2zp · >= 1.1.1 and < 1.1.1zg · >= 3.0.0 and < 3.0.20 · >= 3.3.0 and < 3.3.7 · >= 3.4.0 and < 3.4.5 · >= 3.5.0 and < 3.5.6 · >= 3.6.0 and < 3.6.2

Fixed in: 1.0.2zp, 1.1.1zg, 3.0.20, 3.3.7, 3.4.5, 3.5.6, 3.6.2

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy openssl || rpm -q openssl || openssl --version

2. UPGRADE to 1.0.2zp (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade openssl

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade openssl

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Advisories and coverage

Official advisories

CISA Alerts and Advisories: Hitachi Energy RTU500 Product 2026-10-20

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-28388?

openssl: upgrade to 1.0.2zp, 1.1.1zg, 3.0.20, 3.3.7, 3.4.5, 3.5.6, 3.6.2. Exact commands for each OS are on this page.

Is CVE-2026-28388 being exploited?

CVE-2026-28388 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-28388 affect?

CVE-2026-28388 affects openssl. Severity is high (CVSS 7.5). 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 cr

How urgent is CVE-2026-28388?

Priority 51/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

OpenSSL vulnerabilities

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References

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