CVE-2025-58714: Local Privilege Escalation in Windows AFD WinSock Driver

Microsoft’s security channels added CVE-2025-58714 to the record this week: an elevation‑of‑privilege weakness in the Windows Ancillary Function Driver for WinSock (the afd.sys stack) that — if left unpatched on an affected host — lets a locally authorized attacker raise their process context to SYSTEM. The vulnerability is rated High (CVSS 3.1 — 7.8) and is described by vendors as an improper access control issue in the WinSock ancillary driver; Microsoft’s Security Update Guide is the canonical advisory for remediation mapping.

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Background / Overview​

The Windows Ancillary Function Driver for WinSock (commonly referenced as AFD / afd.sys) provides the kernel‑level plumbing for socket operations, interprocess network I/O, and other low‑level networking primitives. Because it runs inside kernel mode and services userland socket requests, defects in afd.sys have long been high‑value targets for exploit developers: a reliable local privilege escalation in the TCP/IP stack or WinSock driver can turn a low‑privilege foothold into full system compromise. Recent years have seen several afd.sys and WinSock‑adjacent CVEs patched across Windows servicing branches, which makes another entry in that category both unsurprising and consequential.
CVE‑2025‑58714 is listed with a base score of 7.8, vector string indicating a local attack vector, low attack complexity, and low privileges required to begin the exploit attempt — meaning an attacker who can run code as a normal user on the machine may be able to leverage it for privilege elevation. Public vulnerability indexes mirror Microsoft’s severity and summary information.

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What the advisory actually says (quick technical summary)​

• The weakness is described as improper access control in the Windows Ancillary Function Driver for WinSock. The vendor-assigned weakness classification maps to CWE‑284 (Improper Access Control) in published metadata for the CVE.
• Impact: local elevation of privilege — successful exploitation can give the attacker SYSTEM‑level rights on the host (confidentiality, integrity and availability impacts are rated high).
• Attack vector: local (an attacker must execute code on the target machine). There is no official indication in the public advisory that remote exploitation over the network is possible without prior local code execution.
• CVSS vector and base score appear as CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H — this is consistent across multiple CVE aggregators.

Because Microsoft’s Update Guide is the authoritative mapping for which builds and KB packages fix a given CVE, administrators should consult that vendor data via their patch management channel; third‑party trackers reproduce the advisory data, but mapping SKUs and KB numbers is most reliable when pulled from Microsoft’s Update Guide or Update Catalog.

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Technical analysis — how WinSock/AFD weaknesses are abused (what to expect)​

The WinSock ancillary driver exposes a range of control paths from user space into kernel mode, typically through IOCTLs or socket management interfaces. A flaw described as improper access control suggests a code path where the driver performs an authorization check or type/ownership verification incorrectly, allowing a caller to operate on kernel resources they shouldn't control.
Attack classes observed historically in this component include:

• Buffer overflows and off‑by‑one / boundary errors that corrupt kernel memory and redirect execution.
• TOCTOU (time‑of‑check, time‑of‑use) races where an attacker swaps or manipulates a resource between validation and use, creating an escalation primitive.
• Improper pointer/type interpretation or marshaling mistakes that let user‑supplied structures be treated as privileged kernel objects.

Exploit developers typically chain a local code execution foothold (malicious user process, compromised app, or deception like a malicious installer) into a crafted interaction with afd.sys — supplying malformed structures, racing kernel operations, or invoking specific IOCTLs — to produce memory corruption or bypass checks. That corruption is then escalated into overwriting token pointers or spawning SYSTEM processes. Similar AFD/WinSock issues in prior Patch Tuesday cycles were quickly weaponized after proofs‑of‑concept appeared publicly; defenders should assume an experienced attacker can automate exploitation given time and tooling.
Important nuance: the public advisory classifies this particular CVE as improper access control (CWE‑284), which is different from, say, a classic heap overflow. That changes the expected exploit paths: instead of raw memory corruption, an exploit may rely on abusing a privileged operation the driver exposes when ownership/authorization checks are missing or faulty. Still, the ultimate outcome is the same — a process may be able to exercise SYSTEM privileges.

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Is CVE‑2025‑58714 being actively exploited?​

At the time of publication there are no authoritative public reports from vendor advisories or major U.S. government bulletins that state this CVE is under active exploitation. Public CVE aggregators report the advisory and severity but do not list evidence of in‑the‑wild use. That said, absence of a public statement is not proof that exploitation is not occurring: telemetry‑based detection and vendor adjudication of “active exploitation” can lag or be withheld to protect ongoing incident response. Organizations should therefore assume a conservative posture and treat this as a high‑priority remediation if their hosts are exposed or high‑value.

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Immediate operational priorities (what to do now)​

• Identify affected assets quickly. Query your inventory for Windows builds and versions that run the AFD/WinSock driver (afd.sys). Use your EDR/asset management tools to list installed builds and current KBs. Prioritize domain controllers, admin workstations, RDP hosts, and servers that host sensitive workloads.
• Obtain the correct Microsoft update(s). Use your existing patch pipeline (WSUS, SCCM, Intune, or Microsoft Update Catalog) to identify the KB number that maps to your build. Microsoft’s Security Update Guide is the authoritative mapping so reconcile any third‑party tracker differences against it before deployment.
• Test, then deploy fast. For critical privilege‑escalation bugs, many teams run a short test window (24–72 hours) in a representative lab and then push a rapid, staged roll‑out focusing on the most sensitive endpoints first. Maintain a rollback plan and monitor for regressions after the update.

Numbered playbook (concise):

• Inventory & scope: list endpoints, OS builds, and whether afd.sys is in a default configuration.
• Acquire patch: import the correct KB(s) into your management tooling.
• Test on a small canary group with robust telemetry enabled.
• Deploy to high‑value hosts (domain controllers, admin workstations, server management hosts).
• Expand rollout to general endpoints; validate with post‑update checks (build/Kb checks).
• Hunt for indicators of exploitation during rollout (see detection guidance below).

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Temporary mitigations and hardening (if you cannot patch immediately)​

• Do not disable core networking services on production hosts as a broad mitigation: disabling WinSock/AFD will break connectivity and likely cause more operational harm than risk reduction.
• Enforce least privilege: remove unnecessary local admin rights and enforce separate privileged accounts for administrative activities. This reduces the value of local footholds.
• Tighten application allow‑listing and block execution from temporary or user directories to reduce the chance a low‑privilege user can launch a payload that reaches afd.sys.
• For managed environments, raise EDR/anti‑malware telemetry and create hunts for the detection indicators below.

All mitigations are imperfect; the only reliable fix is to apply Microsoft’s security update for the affected builds.

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Detection and hunting guidance​

Early detection matters. Because local privilege escalations often rely on a sequence of noisy events before final SYSTEM takeover, defenders can look for the telltale signs of attempted exploitation:

• Repeated crashes or restarts of network‑related kernel components or the afd.sys driver; watch for service crash events and correlated bluescreen or kernel dump activity.
• Non‑privileged processes spawning child processes that perform privileged operations (creating scheduled tasks running as SYSTEM, writing to HKLM, loading drivers). Track suspicious parent/child process relationships.
• Unexpected token modifications or process token duplication events in EDR telemetry (attempts to duplicate SYSTEM tokens).
• Unusual DeviceIoControl calls from userland processes to afd.sys or other network stack drivers. EDRs that capture kernel IOCTLs and driver interactions can surface anomalous calls.

Hunting checklist (short):

• Export event logs for the Windows Defender Firewall and networking-related services; look for crashes or frequent restarts.
• Query process creation events for non‑admin processes performing privileged writes.
• Inspect kernel crash dumps for indicators of IOCTL abuse against afd.sys.
• Correlate with remote telemetry (VPN logs, RDP sessions) to spot suspicious access concurrent with local exploit attempts.

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Why this matters to enterprises — threat model and impact​

• Attack surface: AFD/WinSock is present on nearly all Windows endpoints and servers by default. That ubiquity increases exposure: even a small number of vulnerable but internet‑isolated systems can be a stepping stone for lateral movement in an enterprise environment.
• Chaining potential: Elevation‑of‑privilege bugs are staples in multi‑stage attacks. An initial remote compromise (phishing, remote code execution in an app, drive‑by download) followed immediately by a reliable local EoP can allow an adversary to gain durable footholds across a network.
• Operational risk: SYSTEM escalation permits attackers to disable endpoint defenses, create persistence, install kernel drivers, and access stored secrets — translating to full‑blown incident response scenarios.

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Critical analysis — strengths and risks in Microsoft’s handling and the wider ecosystem​

Strengths

• Microsoft’s Security Update Guide remains the authoritative source and maps CVEs to KBs and builds; that single‑source model reduces ambiguity for enterprise patch teams when applied correctly. Microsoft has also been improving machine‑readable outputs (CSAF/CSAF metadata) to help automation. These process improvements help defenders accelerate remediation.
• Public scoring and consistent CVSS vectors across trackers make triage easier for SOC teams: this CVE’s vector and impact are clear, enabling prioritized action.

Risks and caveats

• Aggregation lag: third‑party CVE trackers and vulnerability databases sometimes lag or have inconsistent metadata (CPEs, exact affected SKUs). Reliance on replica feeds alone can lead to missed patch targets; always reconcile against Microsoft’s Update Guide.
• Public detail sparsity: vendor advisories intentionally omit exploit‑enabling details. While responsible, that can slow detection tuning because defenders do not always get the exact conditions or IOCTL sequences that an exploit uses. In practice, defenders must rely on telemetry and defensive heuristics while vendors withhold exploit specifics.
• Chaining speed: local EoP bugs are frequently integrated into fast exploitation chains. Once proof‑of‑concept code appears in public repositories or underground feeds, exploitability often jumps quickly. That makes the window between patch release and real attacks a critical period for defenders.

Flagging unverifiable claims

• Several community writeups have in the past conflated WinSock/AFD CVEs with each other (different CVE IDs, different technical root causes). Confirm any quoted technical detail against Microsoft’s advisory and the KB content for your build; treat third‑party writeups as helpful context but not authoritative. When a specific exploit method is claimed in a public post, validate it against vendor changelogs and kernel symbols in a controlled lab before treating it as definitive.

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Testing and verification guidance for patch owners​

• After applying Microsoft’s update on a canary group, validate the fix by confirming the OS build and KB number on patched hosts. Use scripted checks that compare installed KBs against the vendor-provided list.
• If possible, capture a kernel memory dump or trace from a test host both before and after patching to confirm afd.sys behavior changes and to feed into SOC detection rules.
• Revalidate dependent software (third‑party drivers or networking appliances) for driver signing and compatibility issues when updating. Kernel updates occasionally interact with driver loading sequences; plan for short maintenance windows.

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Long‑term recommendations​

• Harden endpoint posture: enforce least privilege, move to strict application allow‑listing, and reduce the number of accounts able to run arbitrary executables. These measures reduce the frequency of initial footholds that can leverage local EoP bugs.
• Improve telemetry coverage: ensure EDR components collect kernel events, device IOCTL activity, and driver interactions where feasible. These signals are often decisive in catching attempts to abuse kernel drivers.
• Patch automation with verification: automate ingestion of Microsoft’s Update Guide/CSAF feeds into your patch pipeline, but keep a manual verification step mapping KBs to build numbers. Automation accelerates deployment; verification avoids accidental mismatches.

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Conclusion​

CVE‑2025‑58714 is another reminder that kernel‑level networking components remain a prime target for attackers because of the high‑impact privilege elevation they can enable. The vulnerability has a High severity rating (CVSS 7.8) and requires a local code execution foothold, but the low attack complexity and potential for SYSTEM compromise make it a priority patch for all Windows environments. Apply the vendor updates for affected builds without delay, tighten local privileges, and enable hunting based on kernel and afd.sys‑related telemetry while rolling updates across your estate. Treat third‑party writeups as useful context, but reconcile every remediation step against Microsoft’s Security Update Guide and your change management policies before production deployment.

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Security teams should treat this advisory as actionable: inventory, patch, monitor, and harden — in that order.

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Source: MSRC Security Update Guide - Microsoft Security Response Center