Source: Microsoft · Limited verification•Last verified: •Collection Degraded
CVE-2026-62815Unknown / EvaluatingCritical (raw)CVSS 9.8
Microsoft QUIC Remote Code Execution Vulnerability
Published: 11 Aug 2026•Last updated: 03 Sept 2026, 12:30 PM IST•Source identifier: Unknown
Dossier completeness: source-provided sections 3 / 3 · rule guidance available. Missing source facts count as incomplete.
CISA KEV catalog
Unknown
KEV status was not determined.
CVSS score
9.8Critical (raw)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Metric sourceMicrosoft MSRC CVRF
EPSS probability
1%0.010
Percentile61st
Weakness type
—
No further CWE recorded
Remediation
Patch status unknown
KB5120242, KB5120229, KB5120233, KB5120228, KB5121003, KB5120994, KB5120240, KB5121000
Why It Matters
Analysis dossierWhy It Matters
Use after free in Microsoft QUIC allows an unauthorized attacker to execute code over a network.
SOC priority
High Severity / Review
Actively exploited
No
Publicly disclosed
Unknown
Risk basis: Critical CVSS without confirmed KEV exploitation
Affected Products & Remediation
12 source-backed productsAffected products and versions (source)
- Windows Server 2022 · version range not provided by source · Microsoft MSRC · Source
- Windows Server 2022 (Server Core installation) · version range not provided by source · Microsoft MSRC · Source
- Windows Server 2025 (Server Core installation) · version range not provided by source · Microsoft MSRC · Source
- Windows 11 Version 25H2 for ARM64-based Systems · version range not provided by source · Microsoft MSRC · Source
- Windows 11 Version 25H2 for x64-based Systems · version range not provided by source · Microsoft MSRC · Source
- Windows 11 Version 23H2 for ARM64-based Systems · version range not provided by source · Microsoft MSRC · Source
- Windows 11 Version 23H2 for x64-based Systems · version range not provided by source · Microsoft MSRC · Source
- Windows 11 Version 24H2 for ARM64-based Systems · version range not provided by source · Microsoft MSRC · Source
- Windows 11 Version 24H2 for x64-based Systems · version range not provided by source · Microsoft MSRC · Source
- Windows Server 2025 · version range not provided by source · Microsoft MSRC · Source
- Windows 11 version 26H1 for x64-based Systems · version range not provided by source · Microsoft MSRC · Source
- Windows 11 Version 26H1 for ARM64-based Systems · version range not provided by source · Microsoft MSRC · Source
Recorded patch / KBKB5120242, KB5120229, KB5120233, KB5120228, KB5121003, KB5120994, KB5120240, KB5121000
Vendor or catalog guidance (source)
- Microsoft MSRC: Install the security update KB5120242 listed by MSRC
- Microsoft MSRC: Install the security update KB5120229 listed by MSRC
- Microsoft MSRC: Install the security update KB5120233 listed by MSRC
- Microsoft MSRC: Install the security update KB5120228 listed by MSRC
- Microsoft MSRC: Install the security update KB5121003 listed by MSRC
Known exploitation (source facts)
Only what a source states. Unknown means no source has said either way; it is not "not exploited".
- CISA KEV
- Unknown
- Exploited (source statement)
- No
- Publicly disclosed (source)
- Unknown
Suggested hunting (rule-based inference)
SecOps Signal recommendation (rule-based inference). These steps are hunting hypotheses from the vulnerability class; they do not state or imply that exploitation occurred here or anywhere.
Matched microsoft-enterprise (Affected product: Windows Server 2022, Vendor: Microsoft); network-unauthenticated (CVSS AV:N, CVSS PR:N, CVSS UI:N)
Exposure
- Identify affected Microsoft products and compare local builds with the MSRC advisory.Telemetry: DeviceTvmSoftwareVulnerabilities · The MSRC product/build mapping establishes applicability. · Rule microsoft-enterprise
- Identify devices reporting this CVE and note which expose the affected service to untrusted networks.Telemetry: DeviceTvmSoftwareVulnerabilities · A network-reachable, no-privilege vector makes internet-facing instances the first exposure question. · Rule network-unauthenticated
Exploitation evidence
- Review the advisory's documented behavior on matching hosts before selecting a hunt.Telemetry: DeviceProcessEvents · Product family alone does not justify a CVE-specific detection. · Rule microsoft-enterprise
Show more (2)
Exploitation evidence
- Review inbound connections to the affected service from unexpected sources since the advisory date.Telemetry: DeviceNetworkEvents · Hunting hypothesis from the CVSS vector; it does not show that exploitation occurred. · Rule network-unauthenticated
Response
- Confirm the source-stated KB or mitigation on matching assets.Telemetry: DeviceTvmSoftwareVulnerabilities · A post-update inventory check verifies remediation. · Rule microsoft-enterprise
CISA KEV Record
CISA KEV status was not determined for this record.
Change History & Source Data
— No recorded material change
- CNA / source
- Unknown
- Record status · verification
- UPDATED · Unknown
- CPE
- Unknown
Evidence & Provenance
Linked by the query's stored exact CVE association. Review required tables and validation status before use.
Detection Hunting Query
Target: DeviceTvmSoftwareVulnerabilities•Defender XDR
Detect endpoints exposed to CVE-2026-62815
Purpose: Exposure assessment (Category: Exposure Check)Why linked: Query metadata names CVE-2026-62815
DeviceTvmSoftwareVulnerabilities| where CveId == "CVE-2026-62815"| project DeviceId, DeviceName, OSPlatform, OSVersion, SoftwareVendor, SoftwareName, SoftwareVersion, CveId, VulnerabilitySeverityLevel, RecommendedSecurityUpdate, RecommendedSecurityUpdateId| sort by VulnerabilitySeverityLevel descSchema Checked · Not runtime validatedSource: SecOps Signal deterministic template · Limited verificationStatic screening: Passed structure and schema checks; tenant execution is not verified.
Correlated briefings
SecOps Signal surfaces public advisory facts only. A missing value means the source has not published it, not that your environment is unaffected. No tenant inventory is connected.