CVE-2026-50491 Overview
CVE-2026-50491 is an out-of-bounds read vulnerability in the Windows Code Integrity DLL (ci.dll). The flaw allows an authorized local attacker to elevate privileges on an affected system. The Code Integrity component enforces driver signing and kernel-mode code verification, making it a sensitive target for local privilege escalation research. Microsoft published the advisory in July 2026, and the issue is tracked under CWE-125 (Out-of-Bounds Read).
Critical Impact
A low-privileged local user can leverage the out-of-bounds read in ci.dll to elevate privileges, undermining kernel integrity guarantees and enabling further post-exploitation activity.
Affected Products
- Microsoft Windows (Code Integrity DLL ci.dll)
- Specific affected Windows builds are enumerated in the Microsoft Security Response Center advisory
- See the Microsoft Security Advisory CVE-2026-50491 for the authoritative product list
Discovery Timeline
- 2026-07-14 - CVE-2026-50491 published to the National Vulnerability Database
- 2026-07-16 - Last updated in NVD
Technical Details for CVE-2026-50491
Vulnerability Analysis
The vulnerability resides in ci.dll, the Windows Code Integrity module responsible for validating driver and kernel-mode binary signatures. An out-of-bounds read occurs when the component reads memory outside the bounds of an allocated buffer during structure parsing. When triggered from a low-privileged local context, the condition can be manipulated to influence integrity checks or leak kernel memory that supports a privilege escalation chain.
The attack vector is local and requires the attacker to already hold low-level access on the target. Attack complexity is high, indicating that reliable exploitation depends on specific runtime conditions or race windows. Successful exploitation impacts confidentiality, integrity, and availability at the operating system level.
Root Cause
The root cause is classified as CWE-125, an out-of-bounds read. ci.dll reads past the intended boundary of a memory buffer while processing attacker-influenced input. Microsoft has not published deep internal details, but the class of defect typically stems from missing bounds validation on length or offset fields consumed during signature or catalog structure parsing.
Attack Vector
An authenticated local attacker invokes code paths in the Code Integrity subsystem that trigger the flawed read. The over-read either exposes adjacent kernel memory or causes state that the attacker chains into a privilege elevation primitive. No user interaction is required, and the vulnerability does not cross a security scope boundary.
No public proof-of-concept exploit is currently available, and CISA has not added CVE-2026-50491 to the Known Exploited Vulnerabilities catalog. The EPSS score at publication is 0.252%.
See the Microsoft Security Advisory CVE-2026-50491 for vendor-supplied technical details.
Detection Methods for CVE-2026-50491
Indicators of Compromise
- No public indicators of compromise have been published for CVE-2026-50491 at this time.
- Unexpected crashes, bug checks, or integrity check failures involving ci.dll on unpatched Windows systems should be treated as suspicious.
- New or unsigned kernel-mode drivers loading shortly after suspicious user-mode activity from low-privileged accounts.
Detection Strategies
- Monitor Windows Event Log for Code Integrity events (Event IDs 3001-3099) that indicate signature validation failures or anomalies.
- Alert on local privilege escalation patterns such as low-privileged processes spawning SYSTEM-level child processes without a legitimate parent chain.
- Correlate crash telemetry referencing ci.dll with authentication and process creation events from the same user session.
Monitoring Recommendations
- Ingest Windows Security, System, and CodeIntegrity operational logs into a centralized analytics platform for retention and correlation.
- Track patch compliance for the affected Windows builds against the Microsoft advisory to identify systems still exposed.
- Baseline normal driver-load activity so that anomalous kernel-mode loads following user-mode exploitation attempts stand out.
How to Mitigate CVE-2026-50491
Immediate Actions Required
- Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-50491 to all affected Windows systems.
- Prioritize patching on multi-user systems, developer workstations, and any host where low-privileged users can execute arbitrary code.
- Audit local account privileges and remove unnecessary interactive logon rights to reduce the attack surface for local privilege escalation.
Patch Information
Microsoft has issued a security update addressing the out-of-bounds read in ci.dll. Consult the Microsoft Security Advisory CVE-2026-50491 for the specific KB article, affected build numbers, and installation guidance. Deploy via Windows Update, WSUS, Microsoft Intune, or Configuration Manager depending on your environment.
Workarounds
- No official workaround has been published. Patching is the recommended remediation path.
- Enforce least-privilege policies and application control (for example, Windows Defender Application Control) to limit which binaries a low-privileged user can execute.
- Restrict local logon and remote interactive access on servers and sensitive endpoints until the patch is deployed.
# Verify patch deployment status on Windows endpoints
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10
# Inspect the installed version of ci.dll to confirm remediation
Get-Item C:\Windows\System32\ci.dll | Select-Object VersionInfo
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
