EUVD-2026-43975
GHSA-45rx-ww54-53rf
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local-only EoP requiring an existing low-priv foothold (AV:L/PR:L) and a memory-corruption race (AC:H), yielding full SYSTEM control with High C/I/A and unchanged scope.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionCVE.org
Use after free in Microsoft Brokering File System allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in the Microsoft Brokering File System (bfs.sys/Bfs component) affects Windows 11 (24H2, 25H2, 26H1) and Windows Server 2025 (including Server Core), where a use-after-free (CWE-416) lets an already-authenticated local attacker corrupt kernel/broker memory to gain SYSTEM-level privileges. Exploitation requires low privileges but high attack complexity, and there is no public exploit identified at time of analysis. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the attacker to already have local, authenticated access with at least low privileges (PR:L) on the affected host and the ability to run code that interacts with the Brokering File System component - there is no remote or unauthenticated vector (AV:L). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 base score is 7.0 (High) with vector AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H, indicating a local-only attack (AV:L) that already requires some privileges (PR:L) and is non-trivial to exploit (AC:H - likely a race condition typical of use-after-free bugs), but yields full High impact to confidentiality, integrity and availability once successful. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who has already gained low-privileged code execution on a Windows 11 or Server 2025 host - for example via phishing, a compromised service account, or a sandboxed app - invokes the Brokering File System through crafted operations to trigger the use-after-free, wins the timing race to reclaim the freed object, and manipulates the dangling pointer to execute code or escalate to SYSTEM. The high attack complexity (AC:H) means the race may need multiple attempts, but success grants full control of the machine. … |
| Remediation | Apply the Microsoft security update for your specific Windows edition - Patch available per vendor advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-49162, which lists the exact patched build numbers for Windows 11 24H2/25H2/26H1 and Windows Server 2025 (including Server Core); consult the MSRC update guide for the KB corresponding to your build rather than relying on a single version string. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all Windows 11 systems (builds 24H2, 25H2, 26H1) and Windows Server 2025 infrastructure to quantify exposure scope and identify critical vs. …
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Same weakness CWE-416 – Use After Free
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External POC / Exploit Code
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