{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-23666", "assignerOrgId": "f38d906d-7342-40ea-92c1-6c4a2c6478c8", "state": "PUBLISHED", "assignerShortName": "microsoft", "dateReserved": "2026-01-14T16:59:33.464Z", "datePublished": "2026-04-14T16:57:53.069Z", "dateUpdated": "2026-04-14T16:57:53.069Z"}, "containers": {"cna": {"title": ".NET Framework Denial of Service Vulnerability", "datePublic": "2026-04-14T14:00:00.000Z", "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:microsoft:.net:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8.0", "versionEndExcluding": "4.8.4801.0"}, {"vulnerable": true, "criteria": "cpe:2.3:a:microsoft:.net:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8.0", "versionEndExcluding": "2.0.50727.9068 & 3.0.30729.9065 & 4.8.4801.0"}, {"vulnerable": true, "criteria": "cpe:2.3:a:microsoft:.net:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.7.0", "versionEndExcluding": "2.0.50727.9068 & 3.0.30729.9065 & 4.7.4141.0"}, {"vulnerable": true, "criteria": "cpe:2.3:a:microsoft:.net:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.7.0", "versionEndExcluding": "4.8.4801.0"}, {"vulnerable": true, "criteria": "cpe:2.3:a:microsoft:.net:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8.1", "versionEndExcluding": "2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0"}, {"vulnerable": true, "criteria": "cpe:2.3:a:microsoft:.net:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.5.0", "versionEndExcluding": "2.0.50727.8982 & 3.0.30729.8976"}]}]}], "affected": [{"vendor": "Microsoft", "product": "Microsoft .NET Framework 3.5", "platforms": ["Windows Server 2012", "Windows Server 2012 (Server Core installation)", "Windows Server 2012 R2", "Windows Server 2012 R2 (Server Core installation)"], "versions": [{"version": "3.5.0", "lessThan": "2.0.50727.8982 & 3.0.30729.8976", "versionType": "custom", "status": "affected"}]}, {"vendor": "Microsoft", "product": "Microsoft .NET Framework 3.5 AND 4.7.2", "platforms": ["Windows 10 Version 1809 for 32-bit Systems", "Windows 10 Version 1809 for ARM64-based Systems", "Windows 10 Version 1809 for x64-based Systems"], "versions": [{"version": "4.7.0", "lessThan": "2.0.50727.9068 & 3.0.30729.9065 & 4.7.4141.0", "versionType": "custom", "status": "affected"}]}, {"vendor": "Microsoft", "product": "Microsoft .NET Framework 3.5 AND 4.8", "platforms": ["Windows 10 Version 1809 for 32-bit Systems", "Windows 10 Version 1809 for ARM64-based Systems", "Windows 10 Version 1809 for x64-based Systems", "Windows 10 Version 21H2 for 32-bit Systems", "Windows 10 Version 21H2 for ARM64-based Systems", "Windows 10 Version 21H2 for x64-based Systems", "Windows 10 Version 22H2 for 32-bit Systems", "Windows 10 Version 22H2 for ARM64-based Systems", "Windows 10 Version 22H2 for x64-based Systems", "Windows Server 2022", "Windows Server 2022 (Server Core installation)"], "versions": [{"version": "4.8.0", "lessThan": 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"Windows Server 2022 (Server Core installation)", "Windows Server 2022, 23H2 Edition (Server Core installation)", "Windows Server 2025", "Windows Server 2025 (Server Core installation)"], "versions": [{"version": "4.8.1", "lessThan": "2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0", "versionType": "custom", "status": "affected"}]}, {"vendor": "Microsoft", "product": "Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2", "platforms": ["Windows Server 2012", "Windows Server 2012 (Server Core installation)", "Windows Server 2012 R2", "Windows Server 2012 R2 (Server Core installation)"], "versions": [{"version": "4.7.0", "lessThan": "4.8.4801.0", "versionType": "custom", "status": "affected"}]}, {"vendor": "Microsoft", "product": "Microsoft .NET Framework 4.8", "platforms": ["Windows 10 Version 1607 for 32-bit Systems", "Windows 10 Version 1607 for x64-based Systems", "Windows Server 2012", "Windows Server 2012 (Server Core installation)", "Windows Server 2012 R2", "Windows Server 2012 R2 (Server Core installation)"], "versions": [{"version": "4.8.0", "lessThan": "4.8.4801.0", "versionType": "custom", "status": "affected"}]}], "descriptions": [{"value": "Concurrent execution using shared resource with improper synchronization ('race condition') in .NET Framework allows an unauthorized attacker to deny service over a network.", "lang": "en-US"}], "problemTypes": [{"descriptions": [{"description": "CWE-755: Improper Handling of Exceptional Conditions", "lang": "en-US", "type": "CWE", "cweId": "CWE-755"}]}], "providerMetadata": {"orgId": "f38d906d-7342-40ea-92c1-6c4a2c6478c8", "shortName": "microsoft", "dateUpdated": "2026-04-14T16:57:53.069Z"}, "references": [{"name": ".NET Framework Denial of Service Vulnerability", "tags": ["vendor-advisory", "patch"], "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-23666"}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en-US", "value": "GENERAL"}], "cvssV3_1": {"version": "3.1", "baseSeverity": "HIGH", "baseScore": 7.5, "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C"}}]}}}

{}

{"cveTags": [], "descriptions": [{"lang": "en", "value": "Concurrent execution using shared resource with improper synchronization ('race condition') in .NET Framework allows an unauthorized attacker to deny service over a network."}], "id": "CVE-2026-23666", "lastModified": "2026-04-14T18:16:44.507", "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": "Primary"}]}, "published": "2026-04-14T18:16:44.507", "references": [{"source": "secure@microsoft.com", "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-23666"}], "sourceIdentifier": "secure@microsoft.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-755"}], "source": "secure@microsoft.com", "type": "Primary"}]}

{"bugzilla": {"description": "dotnet: .NET Framework: Denial of Service via Race Condition", "id": "2458271", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2458271"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.5", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-366", "details": ["A flaw was found in .NET Framework. An unauthorized attacker can exploit a race condition, which is a concurrent execution using shared resources with improper synchronization, to deny service over a network. This vulnerability can lead to a Denial of Service (DoS) for affected systems."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability."}, "name": "CVE-2026-23666", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not affected", "package_name": "dotnet10.0", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not affected", "package_name": "dotnet8.0", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not affected", "package_name": "dotnet9.0", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "dotnet10.0", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "dotnet8.0", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "dotnet9.0", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "dotnet10.0", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "dotnet8.0", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "dotnet9.0", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-04-14T16:57:53Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-23666\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-23666\nhttps://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-23666"], "statement": "Important: A race condition in .NET Framework can lead to a Denial of Service. This flaw allows an unauthenticated attacker to exploit improper synchronization when using shared resources, causing affected systems to become unavailable. This impacts Red Hat Enterprise Linux 8, 9, and 10, as well as Fedora, where .NET is deployed.", "threat_severity": "Important"}

{}