Microsoft has published a security update for CVE-2025-60719, an untrusted pointer dereference in the Windows Ancillary Function Driver for WinSock (afd.sys) that can be abused by a local, authenticated attacker to gain elevated privileges; administrators should treat this as a high-priority Windows security update and apply Microsoft’s patch immediately.
The Windows Ancillary Function Driver for WinSock (commonly called AFD or afd.sys) is a kernel-mode component that implements low-level socket handling for Windows. It mediates requests from user-mode networking APIs into the kernel networking stack, making it a privileged boundary that must correctly validate, marshal, and synchronize user-supplied data. Defects in AFD historically yield high-value exploitation primitives because a successful local exploit often converts a merely compromised user process into full SYSTEM control. Microsoft’s advisory for CVE-2025-60719 describes the issue as an untrusted pointer dereference in the AFD driver. The vendor-assigned CVSS v3.1 base score is 7.0 (High) with the vector string AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H — i.e., a local attack that requires a low-privileged, authenticated user but carries high impact on confidentiality, integrity and availability. The patch was published on November 11, 2025; the Update Guide entry is the authoritative mapping for which Windows SKUs and KB updates remediate the flaw.
Key takeaways:
Short-term telemetry priorities:
Source: MSRC Security Update Guide - Microsoft Security Response Center
Background / Overview
The Windows Ancillary Function Driver for WinSock (commonly called AFD or afd.sys) is a kernel-mode component that implements low-level socket handling for Windows. It mediates requests from user-mode networking APIs into the kernel networking stack, making it a privileged boundary that must correctly validate, marshal, and synchronize user-supplied data. Defects in AFD historically yield high-value exploitation primitives because a successful local exploit often converts a merely compromised user process into full SYSTEM control. Microsoft’s advisory for CVE-2025-60719 describes the issue as an untrusted pointer dereference in the AFD driver. The vendor-assigned CVSS v3.1 base score is 7.0 (High) with the vector string AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H — i.e., a local attack that requires a low-privileged, authenticated user but carries high impact on confidentiality, integrity and availability. The patch was published on November 11, 2025; the Update Guide entry is the authoritative mapping for which Windows SKUs and KB updates remediate the flaw. Why this matters: WinSock as a recurring, high-value target
AFD/WinSock runs in kernel context and is reachable from normal user processes via socket APIs and control IOCTLs. That combination — privileged kernel execution paths exposed to user input — is why WinSock vulnerabilities repeatedly appear in high-severity advisories. Over 2024–2025 a string of AFD issues (heap overflows, use-after-free, race conditions, type confusion) has demonstrated that WinSock code paths are a frequent focus for both researchers and adversaries. Each vulnerability class has different exploitation mechanics, but many end results are the same: SYSTEM-level escalation or kernel control.Key takeaways:
- High operational impact: A local elevation-of-privilege (EoP) in afd.sys can allow attackers to install persistent components, harvest credentials, disable security tools, and move laterally.
- Low initial barrier: The reported Privileges Required is Low, meaning a standard user account—or malware running as that user—can attempt exploitation.
- Patch available: Microsoft has shipped a security update; applying it is the fastest, most reliable mitigation.
What Microsoft says (short, authoritative summary)
Microsoft’s Update Guide entry for CVE-2025-60719 describes the bug as an untrusted pointer dereference in the Windows Ancillary Function Driver for WinSock and maps affected Windows builds to specific KB updates. The vendor's advisory and published updates are the canonical source for remediation details; administrators should use those packages when updating via WSUS, SCCM/ConfigMgr, Intune, or the Microsoft Update Catalog. Independent vulnerability trackers confirm the vendor metadata (CVSS 7.0, local vector, high impact) and list the issue as not remotely exploitable without prior local access at the time of publication. These aggregators also report no public proof-of-concept (PoC) and no confirmed broad in-the-wild exploitation at initial disclosure, although absence of public PoC is not proof an exploit doesn’t exist privately.Technical analysis: what “untrusted pointer dereference” means and how it can be abused
The vulnerability class: untrusted pointer dereference
An untrusted pointer dereference occurs when kernel code dereferences a pointer that can be influenced by an attacker without proper validation of ownership, type, or lifetime. In kernel-mode drivers such as afd.sys, dereferencing an untrusted pointer can let an attacker:- Read or write kernel memory they shouldn’t control.
- Overwrite kernel structures (tokens, object headers, function pointers).
- Redirect execution or corrupt security-critical data to escalate privileges.
Typical exploitation chain (conceptual)
- Initial foothold: Attacker executes code as a non-privileged user (malicious executable, compromised process, or attacker-controlled app).
- Trigger: The attacker crafts socket operations, IOCTLs, or other WinSock interactions that cause afd.sys to process attacker-controlled pointers.
- Dereference: Kernel code erroneously trusts or directly dereferences an attacker-controlled pointer, producing memory corruption or an engineered state that favors escalation.
- Privilege conversion: The corruption is used to manipulate process tokens, spawn a SYSTEM process, or alter kernel object fields—yielding SYSTEM-level context.
- Post-exploit: Persistent implants, credential theft, and defensive tool modifications follow.
Confirmed facts and what remains unverified
Confirmed by vendor and public trackers:- The vulnerability exists in the Windows Ancillary Function Driver for WinSock (afd.sys).
- The reported weakness class is untrusted pointer dereference; the impact is local elevation of privilege.
- Microsoft published security updates for affected Windows builds on November 11, 2025.
- CVSS v3.1 base score is 7.0 with vector AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H.
- There was no public proof-of-concept released at the time Microsoft published the patch; that does not guarantee the absence of private exploitation. Treat a lack of PoC as temporary uncertainty, not safety.
- The exact code path, offsets, and exploit primitives (heap vs stack layout, specific object type, or sequence of IOCTLs) are not disclosed in the advisory; reverse engineering of the patch or researcher write-ups will be necessary to confirm those details.
Affected platforms and patching guidance (operational)
Microsoft’s Update Guide maps CVE-2025-60719 to specific KBs and OS builds; administrators must verify the KB/patch package that applies to their environment and deploy accordingly. Use your enterprise patch pipelines (WSUS, SCCM/ConfigMgr, Intune, or manual updates) and follow a test → pilot → broad rollout pattern tailored to your organization’s tolerance for risk and change control. Practical sequencing:- Identify affected hosts by matching Windows build numbers and afd.sys versions reported in your inventory.
- Deploy the Microsoft update to a representative pilot ring (including domain controllers and admin workstations) within 24–72 hours.
- Validate application and driver file versions; escalate to broad rollout after functional verification.
- For hosts that cannot be patched immediately, apply compensating controls (listed below).
- Patch promptly. The vendor-supplied update is the primary mitigation.
- Harden local privileges. Enforce least privilege and remove unnecessary local admin accounts.
- Restrict interactive logon. Limit which accounts can log on locally or through RDP, especially on servers and jump boxes.
- Monitor EDR/SIEM. Tune telemetry for privilege escalation indicators (see next section).
Detection, hunting, and indicators of compromise
Because the flaw is local and kernel‑level, detection focuses on unusual local activity, abrupt privilege gains, and driver/IOCTL anomalies.Short-term telemetry priorities:
- Unexpected process elevation to SYSTEM from regular user processes (creation of SYSTEM-child processes).
- Abnormal or high-frequency WinSock/AFD invocation patterns from a single process (many concurrent socket control calls or unusual DeviceIoControl sequences).
- EDR alerts for token or handle duplication, suspicious calls targeting afd.sys, or kernel-mode crashes tied to afd.sys.
- Sudden installation of new services or drivers by non-admin accounts.
- Correlate process creation events where the creating process is non‑privileged but the child runs as NT AUTHORITY\SYSTEM.
- Search for DeviceIoControl or IOCTL sequences against afd.sys or socket handles around the time of privilege changes.
- Monitor for repeatable, highly concurrent socket operations coming from a single user process — a hallmark of attempts to win races or to stress a pointer lifetime.
- Add rules that correlate high-frequency socket control operations with process elevation events.
- Maintain a curated set of YARA/EDR signatures for WinSock-related PoC artifacts after authoritative research is published.
- Review past AFD patches and apply detection lessons learned from those disclosures.
Threat and risk analysis: strengths and residual risks
Notable strengths in the vendor response:- Microsoft published a coordinated security update and an Update Guide entry mapping the CVE to Microsoft KBs and builds — the most direct way to close the window of exposure. A vendor patch materially reduces long-term risk when applied broadly.
- Public vulnerability trackers rapidly indexed the advisory, enabling automated vulnerability management tools to flag affected hosts.
- Technical opacity: Microsoft’s advisories intentionally withhold low-level exploit details to reduce short-term weaponization. While sensible, this means defenders cannot yet tune detections to patch diffs or exploit-specific artifacts until researchers publish analysis.
- Patch lag and operational inertia: Large organizations often stage patches across weeks; delay increases the attack surface for targeted adversaries who know WinSock EoPs are valuable.
- Private exploitation: Advanced persistent threat (APT) groups frequently retain private exploit code; the absence of a public PoC is not evidence that exploitation hasn’t already occurred in limited campaigns.
Recommended checklist for Windows administrators (quick, actionable)
- Map affected hosts: query your inventory and identify Windows builds that include the vulnerable afd.sys versions listed in Microsoft’s Update Guide.
- Patch pilot: apply the Microsoft update to a pilot group that includes domain controllers, admin workstations, and VDI hosts within 24–72 hours.
- Full rollout: move to enterprise-wide deployment after validating stability in the pilot ring.
- Compensate where patching is delayed: remove local admin privileges, restrict RDP/interactive logon, and block untrusted installers or macros.
- Monitor and hunt: implement the detection and hunting guidance above; watch for afd.sys crashes and privilege-elevation artifacts for 7–14 days after deployment.
- Maintain post-patch vigilance: once public analyses or PoCs appear, update detection rules and signatures to reflect the newly-known exploit primitives.
For incident responders: what to do if you suspect exploitation
If telemetry suggests a successful local privilege escalation (unexpected SYSTEM process creation, token theft indicators, or afd.sys crash followed by suspicious service installs):- Isolate the affected host from the network to limit lateral movement.
- Capture volatile memory and kernel crash dumps for analysis by your IR team or third-party forensic partners.
- Preserve EDR logs and relevant artifacts (process trees, DeviceIoControl sequences, driver loads), and consider escalation to Microsoft or law enforcement if targeted compromise is suspected.
- Rebuild compromised systems from known-good images after root-cause analysis, rather than relying solely on remediation actions on a potentially backdoored host.
Broader context and historical parallels
AFD/WinSock has been repeatedly targeted in 2024–2025 with multiple CVEs across different memory-safety classes: heap overflows, use-after-free, race conditions, type confusion, and now untrusted pointer dereference vulnerabilities. Each class can produce different exploitation techniques, but they share the same practical consequence: a powerful local escalation primitive that attackers chain after initial footholds. Security teams should treat WinSock advisories as urgent patch priorities given this history.Final assessment and conclusion
CVE-2025-60719 is a significant local privilege escalation vulnerability in afd.sys — a privileged networking kernel component — described by Microsoft as an untrusted pointer dereference and assigned a CVSS v3.1 base score of 7.0. Microsoft released a security update on November 11, 2025 that remedies the flaw; administrators should prioritize mapping the CVE to KBs for their Windows builds and deploying the update through standard enterprise patch channels. While there was no public proof‑of‑concept at disclosure, the combination of low privileges required to launch an exploit and high impact on system confidentiality and integrity makes this a high-risk item for defenders who delay patching. The best immediate actions are to apply Microsoft’s update, harden local access and privilege models, and increase telemetry and hunting for WinSock/afd.sys indicators. This advisory is part of a continuing pattern in which privileged networking subsystems remain an attractive and potent target for attackers; prompt patching, layered defenses, and improved endpoint telemetry remain the most effective mitigations.Source: MSRC Security Update Guide - Microsoft Security Response Center
