NULL Pointer Dereference in OpenSSL Delta CRL Processing
CVE-2026-28388 is a NULL pointer dereference vulnerability in OpenSSL's X.509 certificate verification path when processing delta CRLs. When a delta CRL containing a Delta CRL Indicator extension is processed, OpenSSL fails to verify that the required CRL Number extension is present before dereferencing it. If an attacker supplies a malformed delta CRL in which the CRL Number extension is missing, the affected code can dereference a NULL pointer and crash the application. The issue occurs only when CRL processing and delta CRL processing are enabled during certificate verification. According to the provided advisory text, the vulnerable condition is outside the OpenSSL FIPS module boundary, and the FIPS modules in 3.6, 3.5, 3.4, 3.3, and 3.0 are not affected.
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Impact, mitigation & remediation
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Impact
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Mitigation
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Remediation
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Exploits
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No public exploit code observed for this vulnerability.
Affected products & vendors
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
15 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A specific vulnerability in OpenSSL addressed in Alpine Linux stable releases 3.20.10, 3.21.7, 3.22.4, and 3.23.4.
A NULL pointer dereference when processing a delta CRL in OpenSSL.
A NULL pointer dereference in delta CRL processing that can cause denial of service when malformed CRLs are handled.
NULL pointer dereference when processing a Delta CRL in OpenSSL.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.