FKIE_CVE-2026-21243
Vulnerability from fkie_nvd - Published: 2026-02-10 18:16 - Updated: 2026-06-17 10:18
Severity
Summary
Null pointer dereference in Windows LDAP - Lightweight Directory Access Protocol allows an unauthorized attacker to deny service over a network.
References
| URL | Tags | ||
|---|---|---|---|
| secure@microsoft.com | https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21243 | Vendor Advisory |
Impacted products
| Vendor | Product | Version | |
|---|---|---|---|
| microsoft | windows_server_2019 | * | |
| microsoft | windows_server_2022 | * | |
| microsoft | windows_server_2022_23h2 | * | |
| microsoft | windows_server_2025 | * |
{
"affected": [
{
"affectedData": [
{
"platforms": [
"x64-based Systems"
],
"product": "Windows Server 2019",
"vendor": "Microsoft",
"versions": [
{
"lessThan": "10.0.17763.8389",
"status": "affected",
"version": "10.0.17763.0",
"versionType": "custom"
}
]
},
{
"platforms": [
"x64-based Systems"
],
"product": "Windows Server 2019 (Server Core installation)",
"vendor": "Microsoft",
"versions": [
{
"lessThan": "10.0.17763.8389",
"status": "affected",
"version": "10.0.17763.0",
"versionType": "custom"
}
]
},
{
"platforms": [
"x64-based Systems"
],
"product": "Windows Server 2022",
"vendor": "Microsoft",
"versions": [
{
"lessThan": "10.0.20348.4773",
"status": "affected",
"version": "10.0.20348.0",
"versionType": "custom"
}
]
},
{
"platforms": [
"x64-based Systems"
],
"product": "Windows Server 2022, 23H2 Edition (Server Core installation)",
"vendor": "Microsoft",
"versions": [
{
"lessThan": "10.0.25398.2149",
"status": "affected",
"version": "10.0.25398.0",
"versionType": "custom"
}
]
},
{
"platforms": [
"x64-based Systems"
],
"product": "Windows Server 2025",
"vendor": "Microsoft",
"versions": [
{
"lessThan": "10.0.26100.32370",
"status": "affected",
"version": "10.0.26100.0",
"versionType": "custom"
}
]
},
{
"platforms": [
"x64-based Systems"
],
"product": "Windows Server 2025 (Server Core installation)",
"vendor": "Microsoft",
"versions": [
{
"lessThan": "10.0.26100.32370",
"status": "affected",
"version": "10.0.26100.0",
"versionType": "custom"
}
]
}
],
"source": "secure@microsoft.com"
}
],
"configurations": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:*",
"matchCriteriaId": "B6E3E93E-8160-4BFB-B5CB-85740922CF7E",
"versionEndExcluding": "10.0.17763.8389",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:*",
"matchCriteriaId": "9E19FC4B-C3CC-4924-9A0B-5E4F100280D4",
"versionEndExcluding": "10.0.20348.4711",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:microsoft:windows_server_2022_23h2:*:*:*:*:*:*:*:*",
"matchCriteriaId": "F0EA3C51-C3FE-494A-92D9-D3B1C301CB54",
"versionEndExcluding": "10.0.25398.2149",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:*:*",
"matchCriteriaId": "33AF95F4-504F-40EF-9F64-5D6F7B40114F",
"versionEndExcluding": "10.0.26100.32313",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "Null pointer dereference in Windows LDAP - Lightweight Directory Access Protocol allows an unauthorized attacker to deny service over a network."
},
{
"lang": "es",
"value": "Desreferencia de puntero nulo en LDAP de Windows - Protocolo ligero de acceso a directorios permite a un atacante no autorizado denegar el servicio a trav\u00e9s de una red."
}
],
"id": "CVE-2026-21243",
"lastModified": "2026-06-17T10:18:20.897",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 7.5,
"baseSeverity": "HIGH",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 3.6,
"source": "secure@microsoft.com",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-21243",
"options": [
{
"exploitation": "none"
},
{
"automatable": "yes"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-02-11T15:27:48.672826Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-02-10T18:16:25.480",
"references": [
{
"source": "secure@microsoft.com",
"tags": [
"Vendor Advisory"
],
"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21243"
}
],
"sourceIdentifier": "secure@microsoft.com",
"vulnStatus": "Analyzed",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-476"
}
],
"source": "secure@microsoft.com",
"type": "Secondary"
}
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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