Listen to this Post
How CVE-2026-49789 Works
CVE-2026-49789 is a stack-based buffer overflow vulnerability residing in the Windows NTFS (New Technology File System) component. The flaw exists within an unknown function of the NTFS driver (ntfs.sys) that handles specially crafted file system operations or metadata structures. When a local, authenticated attacker triggers this vulnerability, the improper handling of input data leads to a stack-based buffer overflow condition, classified under CWE-121.
In a stack-based buffer overflow, a buffer allocated on the call stack (typically a local variable or function parameter) is overwritten beyond its allocated boundary. By supplying a maliciously crafted NTFS volume, mount operation, or file attribute, an attacker can cause the vulnerable NTFS function to copy more data into a fixed-size stack buffer than it can hold. This overwrites adjacent stack memory, including critical control structures such as return addresses, exception handler frames, or saved base pointers.
Successful exploitation allows an attacker to hijack the execution flow of the NTFS kernel-mode driver. Since the NTFS driver runs with high integrity (SYSTEM level privileges in the Windows kernel), controlling its execution permits arbitrary code execution in kernel mode. The attacker can then elevate privileges from a standard user to SYSTEM, enabling full compromise of the affected machine — including installation of programs, viewing/altering/deleting data, and creating new accounts with full administrative rights.
The attack vector is local, requiring the attacker to already have valid credentials and the ability to log on interactively or execute code on the target system. However, the attack complexity is low, and no user interaction is required beyond the initial authentication. The vulnerability is not automatable for mass exploitation according to SSVC metrics, but the technical impact is total, meaning a successful exploit results in complete loss of confidentiality, integrity, and availability.
Microsoft assigned a CVSS v3.1 base score of 7.3 (High) with the vector AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H. Third-party analysis from VulDB rates the vulnerability as very critical with a meta score of 8.8 and estimates the current exploit price in the range of $25,000–$100,000. The vulnerability affects a wide range of Windows versions, including Windows 10 (1607, 1809, 21H2, 22H2), Windows 11 (24H2, 25H2, 26H1), and Windows Server up to Server 2025. The CVE was published on July 14, 2026, and the NVD record was last modified on July 15, 2026. As of the publication date, no public exploit is available, and technical details remain undisclosed.
DailyCVE Form:
| Field | Response |
|–|–|
| Platform | Windows NTFS |
| Version | 10.0 / Server |
| Vulnerability | Stack Buffer Overflow |
| Severity | High (7.3) |
| Date | July 14 2026 |
| Prediction | Patch by July 2026 |
What Undercode Say: Analytics
- CVSS v3.1 Base Score: 7.3 (High) – Vector: AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
- CVSS v4.0: NVD assessment not yet provided
- CWE: CWE-121 – Stack-based Buffer Overflow
- EPSS: Not yet available
- SSVC Exploitation: none – Automatable: no – Technical Impact: total
- Exploit Price Estimate: $25k – $100k (as of July 14, 2026)
- CTI Interest Score: 0.69 (elevated interest)
- Affected Products: 18 product configurations across Windows 10/11 and Server editions
- VulDB Meta Score: 8.8 (very critical)
Exploit
As of the publication date, no public exploit is available for CVE-2026-49789. The technical details remain undisclosed, and no proof-of-concept code has been released. However, the following conceptual approach outlines how an attacker might attempt to trigger the vulnerability:
Conceptual steps (no working exploit exists) 1. Craft a malicious NTFS volume with oversized metadata attributes 2. Mount the volume locally or via removable media 3. Trigger the vulnerable NTFS function by accessing a specially crafted file or directory 4. Overwrite the stack return address to redirect execution to shellcode 5. Escalate privileges from user to SYSTEM
Potential exploitation tools and techniques (hypothetical):
Example: Using PowerShell to mount a malicious VHD (conceptual only) Mount-VHD -Path "malicious.vhd" -PassThru | Get-Disk | Initialize-Disk -PassThru | New-Partition -UseMaximumSize | Format-Volume -FileSystem NTFS Example: Triggering the overflow via a crafted alternate data stream (conceptual) echo "malicious_payload" > C:\target.txt:payload
Note: No functional exploit code exists in the wild. Attackers would need to reverse-engineer the vulnerable NTFS function to develop a reliable exploit. The lack of public details and the complexity of kernel-mode exploitation make this a challenging target for casual attackers.
Protection
- Apply Microsoft’s Official Patch: The primary mitigation is to install the July 2026 Patch Tuesday security updates released by Microsoft. Affected versions include Windows 10 (1607, 1809, 21H2, 22H2), Windows 11 (24H2, 25H2, 26H1), and Windows Server up to Server 2025. Update to the following fixed versions:
- Windows 10 1607: ≥ 10.0.14393.9339
- Windows 10 1809: ≥ 10.0.17763.9020
- Windows 10 21H2/22H2: ≥ 10.0.19044.7548 / 10.0.19045.7548
- Windows 11 24H2/25H2: ≥ 10.0.26100.8875 / 10.0.26200.8875
- Windows 11 26H1: ≥ 10.0.28000.2269
- Restrict Local Access: Since the attack requires local authenticated access, enforce the principle of least privilege. Limit user accounts and restrict interactive logon to trusted users only.
- Disable Unnecessary Services: If NTFS mounting of untrusted volumes is not required, consider disabling automatic mounting of removable media or VHD/VHDX files.
- Enable Windows Defender Exploit Guard: Configure Exploit Protection to mitigate stack-based buffer overflows system-wide (e.g., enable “Randomize memory allocations (Bottom-Up ASLR)” and “Validate exception chains (SEHOP)”).
- Network Segmentation: Isolate critical systems and limit lateral movement opportunities. Ensure that local privilege escalation cannot be chained with remote exploits.
- Monitor for Anomalies: Use security information and event management (SIEM) tools to detect unusual NTFS driver activity or unexpected privilege escalations.
- Consider Alternative Products: VulDB suggests that if no patch is available, replacing the affected object with an alternative product may be considered.
Impact
- Confidentiality: An attacker who successfully exploits this vulnerability can read any file on the system, including sensitive user data, system files, and credentials, as the exploit runs in kernel mode with SYSTEM privileges.
- Integrity: The attacker can modify, corrupt, or delete any data on the affected system. This includes altering system files, registry hives, and installed applications, potentially leading to persistent backdoors or system instability.
- Availability: The attacker can cause a system crash (Blue Screen of Death) by corrupting kernel stack memory, leading to denial of service. In a targeted exploit, the attacker could also intentionally crash the system to cover tracks or disrupt operations.
- Privilege Escalation: The primary impact is elevation of privilege from a standard authenticated user to SYSTEM-level access. This allows the attacker to bypass all security boundaries, install malware, create new administrative accounts, and take full control of the machine.
- Lateral Movement: With SYSTEM privileges on one machine, the attacker can use the compromised host as a pivot point to move laterally across the network, potentially compromising additional systems and domain controllers.
- Data Exfiltration: The attacker can exfiltrate sensitive business data, intellectual property, or personally identifiable information (PII) without restriction.
- Persistence: The attacker can install kernel-mode rootkits or bootkits that survive reboots and are invisible to user-mode security tools, making detection and remediation extremely difficult.
- Financial and Reputational Damage: Organizations affected by this vulnerability may face regulatory fines, legal liabilities, loss of customer trust, and significant costs associated with incident response, system restoration, and forensic investigations.
🎯Let’s Practice Exploiting & Learn Patching For Free:
🎓 Live Courses & Certifications:
Join Undercode Academy for Verified Certifications
🚀 Request a Custom Project:
Secure, high-velocity infrastructure and disruptive technological engineering. Contact our engineering team for high-tier development and proprietary systems:
[email protected]
💎 Smart Architecture | 🛡️ Secure by Design | ⭐ Trusted by Thousands
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
