CVE-2026-58613 Overview
CVE-2026-58613 is a use-after-free vulnerability [CWE-416] in the Windows Cloud Files Mini Filter Driver (cldflt.sys). An authenticated local attacker can trigger the flaw to elevate privileges to SYSTEM on affected Windows client and server builds. Microsoft rates the issue HIGH severity with a CVSS 3.1 base score of 7.8. The vulnerability affects Windows 10 (1809, 21H2, 22H2), Windows 11 (24H2, 25H2, 26H1), and Windows Server 2019, 2022, and 2025. No public proof-of-concept code has been released, and CISA has not added the CVE to its Known Exploited Vulnerabilities catalog.
Critical Impact
Successful exploitation grants an authorized local user kernel-level privileges, providing full control over the operating system, installed applications, and stored data.
Affected Products
- Microsoft Windows 10 (1809, 21H2, 22H2) — x86, x64, and ARM64
- Microsoft Windows 11 (24H2, 25H2, 26H1) — x64 and ARM64
- Microsoft Windows Server 2019, 2022, and 2025 — x64
Discovery Timeline
- 2026-07-14 - CVE-2026-58613 published to the National Vulnerability Database
- 2026-07-16 - Last updated in NVD database
Technical Details for CVE-2026-58613
Vulnerability Analysis
The Windows Cloud Files Mini Filter Driver (cldflt.sys) implements the kernel-side logic for the Cloud Files API used by OneDrive and other cloud sync providers. The driver manages placeholder files, reparse points, and callback contexts that track outstanding sync operations. CVE-2026-58613 is a use-after-free condition in this driver, where an object is freed while a pointer to it remains reachable from another code path. When that stale pointer is subsequently dereferenced, the attacker can influence the freed memory to gain arbitrary kernel read/write, leading to local privilege escalation.
Root Cause
The root cause is improper object lifetime management inside cldflt.sys [CWE-416]. A race between the object release path and a concurrent operation that still references the object leaves a dangling pointer in kernel memory. Because the Cloud Files API accepts input from unprivileged user-mode callers through documented placeholder and hydration IOCTLs, a low-privileged process can drive the driver into the vulnerable state without administrative rights.
Attack Vector
Exploitation requires local access and low-privilege authentication on the target host, with no user interaction. An attacker executes a crafted program that issues Cloud Files control calls to trigger the free while a second thread continues to use the freed structure. By spraying kernel pools to reclaim the freed allocation with attacker-controlled data, the attacker converts the use-after-free into a controlled kernel write and elevates to SYSTEM. Technical analysis of the affected code path is documented in the Talos Intelligence Vulnerability Report TALOS-2026-2426.
No verified public exploit code is available. The vulnerability mechanism is described in prose only; refer to the vendor advisory for authoritative details.
Detection Methods for CVE-2026-58613
Indicators of Compromise
- Unexpected loading or crashes of cldflt.sys recorded in System event log entries and WER (Windows Error Reporting) minidumps.
- Bugchecks referencing cldflt.sys in the call stack, particularly BAD_POOL_CALLER (0xC2) or KERNEL_MODE_HEAP_CORRUPTION (0x13A).
- Non-Microsoft or unsigned processes issuing FSCTL_* calls associated with Cloud Files placeholders on hosts that do not use cloud sync clients.
Detection Strategies
- Hunt for low-privileged processes that spawn a SYSTEM-integrity child process shortly after interacting with cldflt.sys handles.
- Correlate kernel crash telemetry with recent process creation to identify exploitation attempts that fail before privilege escalation succeeds.
- Baseline expected Cloud Files driver activity per host and alert on process lineage that deviates from OneDrive or authorized sync providers.
Monitoring Recommendations
- Enable Sysmon Event ID 6 (driver loaded) and Event ID 4 (Sysmon service state) to track integrity of cldflt.sys on managed endpoints.
- Forward Windows kernel bugcheck events (Event ID 1001, BugCheck) to the SIEM for correlation with account context.
- Monitor for creation of new services or scheduled tasks by processes that previously held only medium integrity.
How to Mitigate CVE-2026-58613
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft Security Update Guide for CVE-2026-58613 to all affected Windows client and server builds.
- Prioritize patching of multi-user systems, jump hosts, and Remote Desktop Session Hosts where local users can execute arbitrary code.
- Audit local user and service account inventories to identify accounts that could weaponize a local privilege escalation.
Patch Information
Microsoft has released fixes for all supported affected builds through the standard Windows Update channel. Refer to the Microsoft Security Update Guide for the specific KB article and package version that corresponds to each Windows build.
Workarounds
- No official workaround is published. Disabling the Cloud Files Mini Filter Driver is not supported and will break OneDrive and other cloud sync providers.
- Where patching must be deferred, restrict interactive logon rights and remove local administrator equivalents from standard users to reduce the attack surface.
- Enforce application control (Windows Defender Application Control or AppLocker) to block unapproved binaries from executing on affected hosts.
# Verify installed Windows build and quickly identify hosts still exposed
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"
wmic qfe list brief /format:table
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
