CVE-2025-47991 Overview
CVE-2025-47991 is a use-after-free vulnerability [CWE-416] in the Microsoft Input Method Editor (IME) component that ships with supported Windows client and server releases. An authenticated local attacker can trigger the freed-memory condition to elevate privileges on the target host. Microsoft addressed the flaw in its July 2025 security update cycle. The vulnerability affects a broad range of Windows 10, Windows 11, and Windows Server versions, including Windows Server 2025.
Critical Impact
Successful exploitation grants an authorized local user elevated privileges, with a scope change that can impact confidentiality, integrity, and availability of the host.
Affected Products
- Microsoft Windows 10 (versions 1607, 1809, 21H2, 22H2)
- Microsoft Windows 11 (versions 22H2, 23H2, 24H2)
- Microsoft Windows Server 2016, 2019, 2022, 2022 23H2, and 2025
Discovery Timeline
- 2025-07-08 - CVE-2025-47991 published to the National Vulnerability Database
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-47991
Vulnerability Analysis
The Microsoft Input Method Editor (IME) provides text input services for languages that require character composition, such as Japanese, Chinese, and Korean. IME runs in a privileged context to service input across user sessions and applications. This vulnerability is a use-after-free condition [CWE-416] in the IME component, meaning code paths continue to reference a heap object after it has been released. An authorized local attacker who wins a specific timing window can reclaim the freed allocation and pivot execution into attacker-controlled data.
Microsoft classifies the issue as an elevation-of-privilege bug. Because the vulnerable code executes within a higher-privileged process boundary, successful exploitation crosses a security boundary and yields code execution beyond the caller's original rights.
Root Cause
The root cause is improper object lifetime management inside the IME code path. A reference to a heap-allocated structure remains reachable after the underlying memory is freed. Subsequent operations that dereference the stale pointer read or write memory that may already be repurposed, leading to controlled corruption of adjacent state.
Attack Vector
Exploitation requires local access and valid low-privilege credentials on the target. No user interaction is needed. The attacker triggers IME processing paths and races the free/reuse sequence to place attacker-controlled data into the reclaimed allocation. High attack complexity reflects the need to reliably shape the heap and win the race.
No verified public proof-of-concept code exists in the enriched dataset. Refer to the Microsoft Security Update CVE-2025-47991 advisory for vendor-supplied technical context.
Detection Methods for CVE-2025-47991
Indicators of Compromise
- Unexpected child processes spawned by IME-related binaries or svchost.exe instances hosting text services.
- Local user accounts suddenly executing operations that require elevated tokens without a legitimate elevation event chain.
- Crash telemetry referencing IME modules with access violations consistent with heap corruption.
Detection Strategies
- Hunt for anomalous token manipulation or privilege assignment events originating from standard user sessions.
- Correlate Windows Error Reporting (WER) crash dumps that reference IME components with subsequent privileged process launches from the same session.
- Baseline normal IME process behavior per host and alert on deviations such as unusual thread injections or memory-region allocations flagged as executable.
Monitoring Recommendations
- Enable and forward Sysmon Event IDs 1, 8, 10, and 11 to centralize process, thread injection, process access, and file creation telemetry.
- Monitor Windows Security Event ID 4672 (special privileges assigned) for accounts that should not routinely receive administrative rights.
- Retain crash dumps and application error events (Event ID 1000) that name IME DLLs for retrospective analysis.
How to Mitigate CVE-2025-47991
Immediate Actions Required
- Apply the July 2025 Microsoft security updates that remediate CVE-2025-47991 to all affected Windows 10, Windows 11, and Windows Server systems.
- Prioritize multi-user hosts such as terminal servers, VDI infrastructure, and shared workstations where local-privilege escalation has the largest blast radius.
- Audit local account inventories and remove unused low-privilege accounts that could serve as an initial foothold.
Patch Information
Microsoft has released fixed builds for every affected Windows client and server SKU. Consult the Microsoft Security Update CVE-2025-47991 guidance for the specific KB article and build numbers that correspond to each product version, then deploy through Windows Update, WSUS, Intune, or Configuration Manager.
Workarounds
- No official vendor workaround is documented; patching is the supported remediation path.
- Where patching must be staged, restrict interactive logon rights on high-value hosts to reduce the pool of accounts capable of triggering the local attack path.
- Enforce application control policies (for example, Windows Defender Application Control or AppLocker) to limit unauthorized binaries that could stage exploit code on affected systems.
# Verify installed cumulative update on a Windows host
wmic qfe list brief /format:table
# Or, using PowerShell:
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
