CVE-2026-57093

What it actually does

CVE-2026-57093 is a local privilege escalation vulnerability caused by a use-after-free condition in the Windows Ancillary Function Driver for WinSock, a kernel-mode networking component commonly exposed through Windows socket-related functionality. An attacker who already has valid low-privileged local access can attempt to trigger object lifetime corruption in the driver and potentially execute code in kernel context or otherwise obtain SYSTEM-level privileges. Because the vulnerability is local, it does not provide initial remote access by itself, but it can materially increase the impact of phishing, malware execution, stolen credentials, or exploitation of a separate remote-code-execution flaw.

Why it matters to the business

Successful exploitation could allow an intruder who has already gained limited access to a Windows workstation or server to take full control of the affected system, disable security tools, access sensitive data, dump credentials, move laterally, and deploy additional payloads. The affected product range is broad, covering many supported Windows client and server versions, so organizations with diverse Windows fleets may have significant patching exposure. The CVSS score is high, but current public exploitation signals are low: it is not listed in CISA KEV, is not identified as ransomware-used, has low EPSS, and no public exploit maturity is reported; nonetheless, local privilege escalation bugs are commonly chained after initial compromise and should be remediated through normal high-priority Windows patch cycles.

How an attack unfolds

An attacker first needs code execution or an interactive foothold as a low-privileged authenticated user on an affected Windows system. From that position, they run a purpose-built local exploit that interacts with WinSock/AFD driver functionality to manipulate kernel object allocation and lifetime behavior. If the exploit successfully wins the required timing or memory-layout conditions, the driver references freed memory, allowing the attacker to corrupt kernel memory or redirect execution in a controlled way. The attacker then elevates from a standard user context to SYSTEM or equivalent kernel-level authority. After elevation, they can create privileged processes, dump credentials from memory, tamper with endpoint protection, persist through services or scheduled tasks, and use the compromised host as a platform for lateral movement. The CVSS attack complexity is high, so reliable exploitation may require precise system-state manipulation and version-specific exploit development.

How to fix it

Apply the Microsoft security update that remediates CVE-2026-57093 for all affected Windows versions, including Windows 10 1607/1809/21H2/22H2, Windows 11 24H2/25H2/26H1, Windows Server 2012/2016/2019/2022/2025. No fixed version numbers were provided in the input, so use the applicable July 2026 or later cumulative security update from Microsoft Update, Windows Update for Business, WSUS, Microsoft Configuration Manager, or the Microsoft Update Catalog for each OS build. Prioritize internet-facing servers, shared user systems, VDI/session hosts, developer workstations, domain administration workstations, and systems where untrusted users can execute code. Where immediate patching is not possible, reduce risk by limiting interactive logon rights, removing unnecessary local users, enforcing least privilege, blocking untrusted executable content, enabling attack surface reduction rules, and ensuring endpoint protection is active. Because this is a kernel driver vulnerability, disabling WinSock/AFD is generally not a practical mitigation without breaking normal networking functionality.

How to confirm the fix worked

Confirm that each affected Windows system has installed the Microsoft cumulative update that includes the fix for CVE-2026-57093, using Windows Update compliance reporting, WSUS/Configuration Manager status, endpoint management inventory, or authenticated vulnerability scanning. Validate OS build and installed hotfix state with commands such as `winver`, `systeminfo`, `wmic qfe list`, PowerShell `Get-HotFix`, or enterprise patch-management telemetry, then compare results against Microsoft’s security update guidance for the specific Windows release and build. Re-run vulnerability scans after patch deployment and confirm the finding is closed across representative workstation and server populations. For high-value systems, verify reboot completion after patch installation because kernel driver fixes typically require a restart to take effect.

Typical attack path

1. Obtain initial access to an affected Windows workstation or server through stolen credentials, phishing, malware execution, exposed remote access, or another vulnerability.
2. Establish local code execution as a low-privileged authenticated user.
3. Run a local exploit that exercises Windows Ancillary Function Driver for WinSock functionality and attempts to trigger the use-after-free condition.
4. Manipulate memory layout and timing so the freed kernel object is reused in an attacker-influenced way.
5. Achieve privilege escalation to SYSTEM or kernel-level execution if exploitation succeeds.
6. Disable security controls, access protected files or credentials, install persistence, and continue lateral movement or payload deployment.

How to detect it

This vulnerability is a local kernel privilege escalation, so exploitation may not produce a unique network signature. Detection should focus on endpoint telemetry, Windows Security logs, Sysmon/EDR events, and crash artifacts around suspicious privilege changes. Review events where a low-privileged user process quickly spawns or causes execution of SYSTEM-level processes, creates new services, creates scheduled tasks, modifies local administrator membership, accesses LSASS, disables security tools, or drops unfamiliar binaries in temporary or user-writable directories. Hunt for abnormal process lineage involving network/socket-using test binaries or unknown executables immediately followed by SYSTEM shells, `cmd.exe`, `powershell.exe`, `rundll32.exe`, `regsvr32.exe`, service creation, or credential access. Check Windows crash dumps, WER reports, and system event logs for bugchecks or driver faults involving `afd.sys`, especially near the time of suspicious local execution. Because no public exploit or actor-specific tooling is identified in the input, prioritize behavioral detection over static indicators.

• afd.sys
• Afd
• Microsoft-Windows-WER-SystemErrorReporting
• BugCheck
• Event ID 7045
• A service was installed in the system
• Event ID 4697
• A service was installed in the system
• Event ID 4672
• Special privileges assigned to new logon
• Event ID 4688
• cmd.exe
• powershell.exe
• whoami /priv
• net localgroup administrators
• schtasks /create
• sc.exe create
• lsass.exe
• procdump.exe
• comsvcs.dll
• rundll32.exe comsvcs.dll, MiniDump

What your security team should do

• Patch affected Windows systems through the normal high-priority security update process, prioritizing servers, privileged access workstations, shared systems, and endpoints with broad user access.
• Use asset inventory and vulnerability scanning to identify all affected Windows 10, Windows 11, and Windows Server versions, including legacy or long-term-servicing builds.
• Monitor for suspicious local privilege escalation behavior, especially low-privileged processes spawning SYSTEM-level shells, services, scheduled tasks, or credential-dumping tools.
• Harden endpoints by enforcing least privilege, restricting local administrator membership, enabling Microsoft Defender or equivalent EDR, and applying attack surface reduction rules.
• Investigate any endpoint alerts involving abnormal interaction with kernel drivers, process token manipulation, LSASS access, service creation, or unexpected privilege changes.
• Because EPSS is currently low, the vulnerability is not in CISA KEV, and no public exploit maturity is reported, balance urgency against operational patch windows while still treating it as important due to its post-compromise value.
• Ensure systems are rebooted after patching and track exceptions where reboot deferral could leave the vulnerable driver loaded.