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CVE-2026-21243 is a denial-of-service vulnerability in Windows Lightweight Directory Access Protocol (LDAP) caused by a null pointer dereference. The flaw can be triggered by an unauthorized attacker over the network, indicating that malformed or unexpected LDAP traffic can cause the vulnerable LDAP component to dereference a null pointer and terminate or become unavailable. The issue affects the Windows LDAP service/component and is rated Important with a CVSS score of 7.5.
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What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
7 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A denial-of-service vulnerability affecting Windows LDAP.
A denial of service vulnerability in Windows LDAP (no additional details provided in the content).
A denial-of-service vulnerability in Windows LDAP.
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.