October 13, 2026

CVE Watchtower

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CVE-2026-28388NVD

Vulnerability Summary

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.
Severity Level
HIGH(7.5)
Published Date
Apr 7, 2026
Last Modified
Jul 24, 2026
Exploitation Status
No confirmed exploitation yet
EPSS Score (30-Day)
0.89%Probability
Root Weakness (CWE)
CWE-476: Unknown/Unlisted Weakness ↗
Refer to the official MITRE database for detailed architectural specifications regarding this weakness.
CVSS v3.1 Base Metrics — Score 7.5 (HIGH)
Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone
User InteractionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh

Affected & Patched Versions

Affected Versions
  • Openssl Openssl >= 1.0.2 and < 1.0.2zp
  • Openssl Openssl >= 1.1.1 and < 1.1.1zg
  • Openssl Openssl >= 3.0.0 and < 3.0.20
  • Openssl Openssl >= 3.3.0 and < 3.3.7
  • Openssl Openssl >= 3.4.0 and < 3.4.5
  • Openssl Openssl >= 3.5.0 and < 3.5.6
  • Openssl Openssl >= 3.6.0 and < 3.6.2
Patched Versions
  • Openssl Openssl 1.0.2zp
  • Openssl Openssl 1.1.1zg
  • Openssl Openssl 3.0.20
  • Openssl Openssl 3.3.7
  • Openssl Openssl 3.4.5
  • Openssl Openssl 3.5.6
  • Openssl Openssl 3.6.2
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🎁7-Day Free Trial — Try Pro or Team, no card required.
📧Email Delivery — Threat intel straight to your inbox.
♾️Unlimited Vendors — Track your entire stack.
🚨All New CVEs — Be the first to know.
📈EPSS Spike Alerts — Catch rising risk before it peaks.
🎯Custom EPSS/CVSS — Filter noise, focus on risk.
🛡️Exploit Intel — A 2nd confirmed-exploit signal beyond KEV.
🐙GitHub Issues — Auto-tracked, no duplicates.
📬Weekly Digest — One clean summary, not inbox spam.
🏷️Watchlist Groups — Tag alerts by team (Infra/AppSec/SOC).
💬Webhooks — Slack & Teams integration.
🔀Smart Routing — Critical alerts to one channel, rest to another.
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External References