Microsoft has recorded CVE-2025-62466, a Windows Client‑Side Caching (CSC, aka Offline Files) elevation‑of‑privilege vulnerability that the vendor lists in its Security Update Guide and which public CVE aggregators are currently scoring as
High (CVSS v3.1 = 7.8); the entry describes a
null pointer dereference inside the CSC service that can be abused by an authorized local user to escalate privileges on an affected host.
Background / Overview
Client‑Side Caching (CSC) — surfaced to users as
Offline Files — is the Windows subsystem that caches network file shares locally (cache directory typically under C:\Windows\CSC) so users can continue working when disconnected from the network. CSC service components run with elevated privileges and perform privileged file operations on cached content and synchronization metadata; that privileged context makes bugs in CSC particularly attractive for local attackers seeking system‑level control. Public and community reporting for CSC‑class CVEs over 2024–2025 shows a repeating pattern: logic or file‑handling flaws, race conditions, symlink/reparse abuses and improper access checks frequently yield reliable elevation‑of‑privilege (EoP) primitives when the privileged service is coerced into acting on attacker‑controlled files or paths.
Microsoft’s MSRC entry for CVE‑2025‑62466 is terse (typical of initial vendor advisories) but confirms the vulnerability affects the Windows Client‑Side Caching service and allows a local, authorized attacker to elevate privileges. Independent vulnerability aggregators (which mirror vendor advisories) currently list a CVSS v3.1 base score of
7.8 with the vector consistent with a
local attack that requires only low privileges to start. At the time of writing, public vendor documentation is limited and canonical per‑SKU KB mappings may require interactive lookups on Microsoft’s Update Guide.
Technical summary — what the public record says
The bug class and immediate mechanics
- The public descriptor for CVE‑2025‑62466 identifies a null pointer dereference (CWE‑476) in the CSC service. A null pointer dereference typically causes a crash, but in some contexts can be triggered in a way that yields a more powerful primitive (for example, if it can be combined with another condition to influence control flow or object layout). Aggregated trackers classify the defect as enabling local privilege escalation when exploited against the privileged CSC service.
Attack vector and preconditions
- Attack vector: Local (attacker must already have some form of authorized local account or ability to execute code locally).
- Privileges required: Low (a non‑privileged user can trigger the condition).
- User interaction: Not required beyond the attacker’s local access.
- Impact: High on confidentiality, integrity and availability if exploitation succeeds — the practical worst case is SYSTEM‑level control. These characteristics mirror prior CSC advisories and published exploitability models.
What’s verifiable now
- Microsoft has an MSRC Update Guide entry for CVE‑2025‑62466. The vendor entry confirms vulnerability existence but does not publish a detailed technical writeup in that page (common for early advisories).
- Public CVE mirrors have added the CVE and list the weakness as a null pointer dereference with CVSS 7.8. That corroboration increases confidence that the vulnerability is real and that the summary in the MSRC Update Guide accurately represents the problem as Microsoft assessed it.
What is not (yet) verifiable
- There is no authoritative published proof‑of‑concept exploit in widely‑trusted public repositories at the time of writing. Aggregators and vendor mirrors do not show public exploit code tied to CVE‑2025‑62466. That may change rapidly — historically, once a detailed patch or PoC appears, weaponization follows quickly. Treat the absence of PoC as provisional, not reassuring.
- Canonical NVD/Mitre enrichment and per‑SKU KB mapping may lag vendor pages or aggregator mirrors; administrators should consult Microsoft’s Update Guide interactively to obtain the exact KB → OS build mapping for their environment.
Why CSC bugs are high‑value for attackers
The CSC service is a classic EoP target for several reasons:
- CSC runs privileged operations on cached files and metadata; when a privileged service performs IO on attacker‑controlled paths or intermediates, TOCTOU and symlink/reparse primitives become possible.
- Offline Files cache and sync workflows touch both user and system data stores; manipulating the cache can create pathways to replace files, inject executables, or obtain sensitive handles.
- A local EoP that converts a low‑privileged foothold into SYSTEM is a force multiplier for attackers — enabling credential theft, disabling detection agents, and lateral movement across the enterprise.
- The CSC attack surface is present across many Windows SKUs (desktop and some server features), increasing blast radius in heterogeneous environments. These operational themes are reinforced by multiple CSC advisories and community write‑ups covering earlier 2025 CSC vulnerabilities and remediation patterns.
Practical risk assessment
Likelihood of exploitation
- Because the vector is local, exploitation requires an initial local foothold (for example, malicious code executed under a standard user account, or a low‑privileged attacker with physical or remote interactive access).
- The ease of turning a null pointer dereference into a reliable elevation primitive varies by bug; some null dereferences are only crash‑causing, while others can be part of a chain that yields code execution. Given the high privileged context of CSC, even crash‑based denial‑of‑service or forced restarts can be operationally significant. Current public information does not state confirmed exploitation in the wild for CVE‑2025‑62466.
Potential impact on enterprise estates
- If weaponized, an attacker can pivot from a local user account to SYSTEM on affected hosts — enabling:
- Tampering with security tooling and kernel modules,
- Harvesting credentials and secrets,
- Deploying persistence and lateral movement tools,
- Manipulating cached content or build artifacts on developer machines or build servers that use Offline Files.
Operational urgency
- Elevation‑of‑privilege vulnerabilities are high priority for enterprises because they are often used in post‑compromise stages. However, the immediacy of remediation should be prioritized based on exposure: servers and systems where untrusted local code execution is possible (public kiosks, shared workstations, build machines, admin jump boxes) should be treated as a higher patching priority.
Recommended mitigations — short term and long term
The single most reliable mitigation for a confirmed Microsoft EoP advisory is vendor patching. Beyond that, apply layered compensations while you validate and deploy updates.
Immediate (0–72 hours)
- Confirm the CVE → KB → OS build mapping for every Windows build in your estate using Microsoft’s Security Update Guide (MSRC). Do not assume a single KB will apply to all SKUs.
- Prioritize patching hosts where an attacker could gain local code execution or where Offline Files is enabled (VDI pools, shared workstations, build machines, admin boxes).
- Where patching is delayed, consider temporarily disabling Offline Files / CSC on hosts that do not require it:
- Disable the Offline Files feature via Group Policy or Settings for managed clients.
- Stop and set the CSC/CscService to manual or disabled in tightly controlled maintenance windows, acknowledging functional loss. Past CSC advisories recommend this temporary measure when immediate patching is impossible.
- Restrict local administrative rights and employ least privilege controls to limit the utility of a local foothold.
- Increase telemetry and hunts: look for anomalous behaviors such as unexpected writes under C:\Windows\CSC, unexpected service restarts or crashes, and sudden SYSTEM‑context process creation following local user activity.
Medium term (3–14 days)
- Deploy tested updates across the fleet via WSUS, SCCM/ConfigMgr, Intune or your patching pipeline; validate builds and require reboots where KBs mandate them.
- Tune EDR/SIEM to detect local privilege escalation patterns: token duplication attempts, new service/service binary changes, scheduled task creation, and suspicious child processes spawned by privileged services.
- Use application allow‑listing (WDAC/AppLocker) to prevent arbitrary executables from running in locations writable by non‑privileged users.
Long term
- Harden the local environment to reduce local attack surface:
- Reduce local admin counts,
- Enforce code integrity policies,
- Block execution from predictable user‑writable paths,
- Instrument offline files usage and minimize the number of hosts that enable the feature by default.
- Review development and build host protections: treat dev/build hosts with elevated access as tier‑1 assets and isolate them from user‑facing desktops. Historical CSC findings show build systems can be high‑value targets.
Detection and incident response playbook
- Hunt signals:
- Service Control Manager (SCM) events showing CSC/CscService crashes or restarts shortly before suspicious activity.
- EDR alerts indicating processes spawned by privileged service contexts (unexpected cmd.exe/PowerShell children).
- Unexpected file creation/overwrite in system paths proximate to cache sync times (C:\Windows\CSC and related shadow locations).
- Collect and preserve volatile evidence (memory snapshots, full EDR logs, Windows Event logs) before remediation if exploitation is suspected.
- If compromise is confirmed:
- Isolate the host from the network,
- Capture full forensic evidence,
- Rebuild from known‑good images if integrity cannot be assured,
- Rotate any credentials or signing keys that may have been exposed. These steps reflect operational guidance derived from past CSC incidents.
How defenders should validate fixes
- Map CVE → KB → OS build precisely (vendor KB is the canonical deployment artifact). After installing the patch, validate the OS build number and the presence of the KB in Update History or via tooling such as:
- Windows Update logs and Get‑HotFix/Get‑HfNetCfg (where applicable),
- WSUS/SCCM reporting, or
- The Microsoft Update Catalog.
- Do not rely solely on aggregator pages or CVE strings when automating patch acceptance; prior incident reviews show CVE → KB mappings sometimes vary by SKU and build.
Strengths and limitations of the public disclosures
Strengths
- Vendor acknowledgement in the Microsoft Security Update Guide provides high confidence the vulnerability exists and is being addressed. The MSRC entry is the authoritative start point for remediation.
- Independent aggregators reflecting the MSRC data — and assigning a CVSS of 7.8 — offer corroboration that the community and third‑party trackers have ingested the advisory and scored the impact consistently. That double‑sourcing increases operational confidence.
Limitations and risk notes
- Vendor entries for CVE disclosures are often terse; MSRC pages sometimes require interactive browsing to reveal full KB mappings or additional metadata. That interactive dependency increases the risk of mis‑patching if administrators rely on non‑authoritative mirrors. Confirm KB mapping directly in the vendor tooling.
- Null pointer dereferences can range from crash‑only issues to exploitable primitives when combined with other conditions. The public descriptions for CVE‑2025‑62466 do not, at the time of writing, include exploitation details or PoC, so the exact exploitation complexity remains uncertain. Treat exploit‑absence conservatively; historically, PoCs and exploit patterns often appear after patch diffs are published.
- Some third‑party trackers can conflate similar CSC advisories or reuse common language across multiple CVEs; defenders must cross‑check per‑SKU details rather than assuming a single remediation step covers all affected builds. Past community notes emphasise this point.
Context: how this fits into recent Windows EoP trends
The 2024–2025 Windows vulnerability landscape has seen repeated prioritized fixes for privileged inbox services and file/caching subsystems (CSC, Broadcast DVR, telemetry/CEIP agents, etc.. The recurring engineering pattern has been privileged services accepting or processing inputs from less‑privileged contexts, creating file‑handling, lifecycle, and access‑control weaknesses that adversaries chain into privilege escalation. CVE‑2025‑62466 sits in this family of issues and reinforces the operational lesson that reducing the local attack surface and applying least privilege are essential complements to patching.
Action checklist for IT teams (concise)
- Confirm whether Offline Files / Client‑Side Caching is enabled across your estate.
- Query Microsoft’s Security Update Guide for CVE‑2025‑62466 → KB mapping for each OS build and plan patching in prioritized waves.
- Temporarily disable Offline Files on systems that don’t require it if you cannot patch immediately.
- Harden endpoints: remove unnecessary local administrator rights, enable allow‑listing, and block execution from user‑writable paths.
- Tune detection: watch for CSC service crashes, unexpected service‑spawned processes, and suspicious writes under C:\Windows\CSC or other system paths.
- If suspicious activity is detected, collect memory and logs, isolate affected hosts, and treat them as potential incidents.
Final analysis: what to expect next
- Expect incremental updates to the MSRC entry and, in short order, expanded tracking by NVD/Mitre and commercial vendors. When vendor KBs and patch binaries are published, security researchers commonly publish deeper technical analyses or PoC demonstrations; that can accelerate weaponization. The prudent operational stance is to patch quickly, validate KB installation, and harden local controls for systems where Offline Files is enabled.
- If you operate a security or patch management program, map and prioritize this CVE as an elevation‑of‑privilege risk and ensure your IR playbooks are prepared to preserve forensic data should an exploitation signal appear. Community and vendor reporting on earlier CSC advisories provides practical detection heuristics and mitigation recipes that apply here.
CVE‑2025‑62466 is a reminder that privileged platform services which bridge user and system contexts — like Client‑Side Caching — remain a high‑value target for adversaries. The vendor acknowledgement and independent mirrors converge on a high‑severity rating and a local EoP attack vector; administrators should treat unpatched hosts as high risk, prioritize mapping CVE → KB precisely, and apply compensating controls where immediate patching is infeasible.
Source: MSRC
Security Update Guide - Microsoft Security Response Center