Microsoft has recorded CVE-2025-62213 as a use‑after‑free elevation‑of‑privilege in the Windows Ancillary Function Driver for WinSock (afd.sys), a kernel‑mode networking component, and administrators are urged to apply the vendor's security update immediately to close a local post‑compromise escalation path that can yield SYSTEM‑level control.
The Windows Ancillary Function Driver for WinSock — commonly called AFD or afd.sys — implements low‑level socket management and mediates requests between user‑mode networking APIs and kernel networking subsystems. Because AFD runs in kernel context and is reachable from normal user processes through well‑documented socket and IOCTL paths, vulnerabilities in this component have outsized operational impact: a successful local exploit can convert a standard user foothold into full system compromise. Community and vendor advisories over 2024–2025 have repeatedly flagged AFD/WinSock as a high‑value target for privilege escalation.
AFD vulnerabilities historically fall into a few recurring classes: use‑after‑free, heap/buffer overflows, race conditions and improper access control/type confusion. Each class can lead to different exploitation strategies — from reliable token manipulation to memory corruption that spawns a SYSTEM process — but the end result for defenders is the same: a compelling post‑compromise primitive that frequently appears in multi‑stage intrusion chains. Public vulnerability trackers and security vendors have cataloged multiple AFD‑related CVEs during the year; CVE‑2025‑62213 joins that family and should be treated with the same urgency.
Source: MSRC Security Update Guide - Microsoft Security Response Center
Background
The Windows Ancillary Function Driver for WinSock — commonly called AFD or afd.sys — implements low‑level socket management and mediates requests between user‑mode networking APIs and kernel networking subsystems. Because AFD runs in kernel context and is reachable from normal user processes through well‑documented socket and IOCTL paths, vulnerabilities in this component have outsized operational impact: a successful local exploit can convert a standard user foothold into full system compromise. Community and vendor advisories over 2024–2025 have repeatedly flagged AFD/WinSock as a high‑value target for privilege escalation.AFD vulnerabilities historically fall into a few recurring classes: use‑after‑free, heap/buffer overflows, race conditions and improper access control/type confusion. Each class can lead to different exploitation strategies — from reliable token manipulation to memory corruption that spawns a SYSTEM process — but the end result for defenders is the same: a compelling post‑compromise primitive that frequently appears in multi‑stage intrusion chains. Public vulnerability trackers and security vendors have cataloged multiple AFD‑related CVEs during the year; CVE‑2025‑62213 joins that family and should be treated with the same urgency.
What Microsoft and public trackers say about CVE‑2025‑62213
Summary of the advisory
Microsoft’s advisory metadata and multiple third‑party aggregators classify CVE‑2025‑62213 as a use‑after‑free vulnerability in the Windows Ancillary Function Driver for WinSock that can be exploited by an authorized local attacker to elevate privileges to SYSTEM. Public trackers list the base CVSS v3.1 score as 7.0 (Important/High) with an attack vector of Local, Privileges Required: Low, and User Interaction: None.Confirmed vendor action
Microsoft has published a security update to remediate the issue and administrators should map the CVE to the appropriate KB(s) for their Windows versions using the Microsoft Security Update Guide (the vendor’s canonical mapping). The presence of an official patch materially reduces the long‑term risk, provided organizations roll it out promptly and verify successful installation. Note: the vendor’s public advisory intentionally omits low‑level exploit details to slow short‑term weaponization.Exploit status and public proofs
At the time the public records were indexed, there was no authoritative public proof‑of‑concept (PoC) or confirmed broad in‑the‑wild exploitation tied explicitly to CVE‑2025‑62213. That absence is not a guarantee of safety: well‑resourced adversaries and targeted campaigns frequently keep exploit code private. Defenders should therefore assume a conservative posture and remediate promptly.Technical snapshot: what “use‑after‑free in afd.sys” implies
How AFD is reachable from user mode
AFD exposes control points from user space — socket options, control IOCTLs and management APIs — which are marshalled into kernel paths in afd.sys. When privileged kernel code keeps or manipulates pointers to user‑supplied objects without robust lifetime management, a use‑after‑free (UAF) can occur: an attacker frees an object and causes the kernel to later dereference that same memory, now under attacker control. Depending on the code paths involved, a UAF in a privileged component like AFD can be escalated into:- arbitrary kernel memory reads/writes,
- corruption of kernel objects (including process tokens),
- hijacked control flow that spawns processes at SYSTEM context.
CVSS and exploitability nuance
The public CVSS vector for CVE‑2025‑62213 reflects a local attack with low privileges required but an attack complexity that some trackers report as high — meaning exploitation may demand precise timing, multi‑threaded triggers, or particular heap grooming techniques. That nuance matters: a low starting privilege combined with higher exploitation complexity still makes the bug a useful second‑stage primitive in real intrusions, especially after initial access techniques (phishing, malicious installers, or compromised user apps) provide the foothold.Practical impact and attacker scenarios
A local EoP in afd.sys can enable several hostile outcomes:- Full endpoint takeover: a process running as a normal user could, if exploitation succeeds, run as SYSTEM and disable protections, install persistent services or drivers, and harvest credentials.
- Privilege chaining: adversaries commonly combine remote initial access (e.g., RCE via other vulnerabilities) with a local EoP to establish durable control within an environment.
- Targeted intrusions: for high‑value targets, attackers may invest the extra engineering to weaponize a high‑complexity UAF because the payoff is full system compromise.
Detection, hunting and compensating controls
Short‑term telemetry priorities
Security teams should add or tune hunts for the following behaviors immediately:- sudden process elevation to SYSTEM from user processes (creation of SYSTEM children by non‑SYSTEM parents),
- abnormal DeviceIoControl or IOCTL sequences that target afd.sys or WinSock driver interfaces,
- concurrent high‑frequency WinSock/AFD invocations from a single process (indicative of race/win‑timing attempts),
- EDR indicators of handle duplication, token impersonation/manipulation, or unexpected kernel memory corruption symptoms.
Compensating controls while you patch
If immediate patching is not possible for all hosts, implement these risk‑reducing steps:- Reduce the set of accounts allowed interactive local or RDP logon on critical servers.
- Remove persistent local administrative rights from daily accounts; require separate elevated admin sessions.
- Enforce application allow‑listing or blocklisting for high‑risk processes that could be used to stage the exploit.
- Increase EDR sensitivity for post‑exploit behaviors and extend alerting windows during the patch rollout period.
Validate patch success
After deploying vendor updates, verify that the updated afd.sys (or associated KB) is present and that each host reports the expected KB installation. Use patch management tools (WSUS, SCCM/ConfigMgr, Intune) and spot‑check driver file versions on high‑value endpoints. Maintain heightened monitoring for 7–14 days after rollout — historical community playbooks show this window is when proof‑of‑concept code or exploit automation commonly appears.Vendor response: strengths and residual risks
Notable strengths
- Patch published: Microsoft released an update that addresses CVE‑2025‑62213; the vendor patch is the single most effective mitigation.
- Rapid indexing: Public trackers and vulnerability databases have quickly listed the advisory and CVSS metadata, allowing enterprise vulnerability management tooling to prioritize targets.
- Authoritative guidance available: Administrators can map the CVE to KB articles with Microsoft’s Security Update Guide — critical for accurate, environment‑specific remediation.
Potential risks and caveats
- Exploit publication may follow the patch: Skilled researchers often reverse‑engineer vendor patches; proof‑of‑concepts and exploitation frameworks tend to surface after a fix is published, increasing the urgency to patch before PoCs are widely distributed.
- Patch rollout inertia: Large enterprises commonly stagger updates for stability testing. That operational reality expands the window of exposure for slower rings and should drive prioritization of admin workstations, domain controllers and jump boxes.
- Visibility gaps: Not all EDRs may detect early exploitation attempts against afd.sys without fine‑tuned IoC and behavioral rules; teams need proactive hunts rather than relying solely on signature updates.
Verified technical specifics and evidence checks
The most load‑bearing technical claims for CVE‑2025‑62213 — vulnerability class (use‑after‑free), affected component (Windows Ancillary Function Driver for WinSock / afd.sys), impact (local elevation of privilege to SYSTEM), CVSS base score (~7.0) and vendor remediation (security update published) — are corroborated by multiple independent trackers and vendor metadata. Feedly’s CVE entry summarizes the vulnerability as a use‑after‑free and lists CVSS v3.1 metrics consistent with public feeds. Malware.news and similar bulletin aggregators independently list CVE‑2025‑62213 in November’s security update rollups as an Important EoP with a score of 7.0 and no public PoC at indexing time. Important verification notes and caveats:- Microsoft’s public advisory text intentionally omits low‑level exploit steps; therefore any claim that the vulnerability is a specific memory correlate (exact function, offset or kernel object) is unverifiable until researchers publish a vetted technical analysis or Microsoft releases detailed patch diffs. Treat such low‑level claims as speculative until confirmed.
- National vulnerability databases (NVD) and vendor pages may lag in enrichment and mapping; rely on Microsoft’s Update Guide for authoritative KB mappings and on your own inventory tools for matching affected SKUs.
Recommended operational playbook (prioritized)
- Map: Query your environment for Windows builds and SKUs that match Microsoft’s affected list — use centralized inventory and patch management to produce a prioritized host list.
- Pilot: Deploy the Microsoft update to a small pilot group that includes domain controllers, admin workstations and known management endpoints within 24 hours.
- Rollout: Expand the rollout to critical systems within 72 hours and complete enterprise‑wide deployment as soon as stability is validated.
- Compensate: For systems that cannot be patched immediately, restrict local logon, remove unnecessary local admin rights and enforce application allow‑listing.
- Hunt: Run targeted EDR/SIEM hunts for symptoms described earlier and monitor for new PoC disclosures or suspicious afd.sys‑targeting activity.
- Verify: Confirm KB and driver file versions, record compliance metrics and reopen any failed deployments for remediation.
Why this matters to Windows administrators and security teams
- Practical exploitation model: While the vulnerability is local, the low privileges required to begin an exploit (standard user) make it an attractive second‑stage primitive in real‑world intrusion campaigns. A seemingly minor initial foothold can escalate into full compromise quickly when chained with an AFD EoP.
- Wide presence of the component: AFD runs on client and server SKUs broadly deployed in enterprise fleets, increasing the operational impact of delayed patching.
- High value to attackers: Even if exploitation is technically complex, the payoff (SYSTEM) justifies the investment for many adversaries — especially those targeting high‑value networks or using multi‑stage campaigns.
Final assessment and headline takeaways
- CVE‑2025‑62213 is a confirmed use‑after‑free in the Windows Ancillary Function Driver for WinSock (afd.sys) that can enable local elevation of privilege to SYSTEM; multiple independent trackers and vendor metadata assign a CVSS v3.1 base score of approximately 7.0.
- Microsoft has published security updates that address the issue; applying the vendor patches is the most effective mitigation. Administrators should map the CVE to the appropriate KB(s) via Microsoft’s Update Guide and prioritize deployment to domain controllers, admin workstations and other high‑value endpoints.
- There was no authoritative public PoC or confirmed mass exploitation at indexing time, but that does not remove urgency: PoCs commonly appear after patches, and attackers routinely use local EoP bugs as post‑compromise escalations. Treat the advisory as high priority and proceed accordingly.
Source: MSRC Security Update Guide - Microsoft Security Response Center
