CVE-2026-62840 – Linux Kernel Elevation of Privilege Vulnerability

CVE-2026-62840 is a Critical elevation of privilege vulnerability affecting the Linux Kernel, specifically the Microsoft MANA Network Driver. The vulnerability exists because of a Time-of-Check Time-of-Use (TOCTOU) race condition that could allow an attacker with limited local privileges to gain SYSTEM-level access. Successful exploitation could compromise system confidentiality, integrity, and availability. Although exploitation requires precise timing and is considered less likely, the potential impact is significant. Microsoft has identified an official fix, and organizations should prioritize remediation to reduce the risk of unauthorized privilege escalation.

CVSS SCORE: 7.0

SEVERITY: Critical

Threat

This vulnerability presents a serious security risk because an attacker with low-level privileges could potentially escalate their access to SYSTEM privileges.

An attacker who successfully exploits this weakness could gain extensive control over an affected system, potentially accessing sensitive information, modifying critical configurations, or disrupting essential services.

The vulnerability requires local access and involves a race condition, making exploitation technically challenging. However, the absence of any user interaction requirement increases the potential risk once an attacker has established limited access.

The vulnerability has a high impact on confidentiality, integrity, and availability, meaning successful exploitation could result in significant system compromise.

Exploits

CVE-2026-62840 has not been publicly disclosed, and no active exploitation has been reported.

The exploitability assessment classifies this vulnerability as “Exploitation Less Likely.”

The exploit code maturity is classified as Unproven, meaning there is no confirmed working exploit.

The vulnerability requires an attacker to successfully exploit a race condition, which increases the technical difficulty of exploitation.

There is no confirmed evidence of publicly available proof-of-concept (PoC) exploit code or zero-day exploitation.

Despite the lack of confirmed exploitation, the potential to obtain SYSTEM privileges makes this vulnerability an important security concern.

Technical Summary

CVE-2026-62840 is a Time-of-Check Time-of-Use (TOCTOU) race condition vulnerability in the Linux Kernel, affecting the Microsoft MANA Network Driver.

A TOCTOU vulnerability occurs when a system checks a condition or resource and subsequently uses it without ensuring that the condition remains unchanged.

An attacker may attempt to manipulate the timing between these operations to exploit the resulting inconsistency.

For this vulnerability, an authorized local attacker with low privileges could attempt to win the race condition and elevate their privileges.

Successful exploitation could grant the attacker SYSTEM-level privileges, potentially allowing them to perform operations beyond their originally authorized access.

The vulnerability has the following technical characteristics:

• Attack Vector: Local — The attacker must have local access to the affected system.
• Attack Complexity: High — Successful exploitation requires winning a race condition.
• Privileges Required: Low — The attacker needs limited existing privileges.
• User Interaction: None — No additional user interaction is required.
• Scope: Unchanged — The security impact remains within the affected security authority.
• Confidentiality Impact: High — Sensitive information could be exposed.
• Integrity Impact: High — Critical system information or configurations could be modified.
• Availability Impact: High — System operations could potentially be disrupted.

An official fix has been identified for this vulnerability.

Exploitability

The vulnerability affects the Linux kernel – Microsoft MANA Network Driver.

The specific affected software versions and fixed build numbers are not confirmed.

Exploitation requires local access with low privileges and successful manipulation of a race condition.

No user interaction is required.

Although exploitation is considered less likely because of its high complexity, a successful attack could result in SYSTEM-level privileges.

Business Impact

CVE-2026-62840 poses a significant risk to organizations operating affected Linux systems using the Microsoft MANA Network Driver.

If successfully exploited, an attacker could potentially gain elevated privileges and compromise critical system resources.

Key business risks include:

• Unauthorized System Control: Attackers could gain SYSTEM privileges, allowing them to perform highly privileged operations.
• Sensitive Data Exposure: Elevated access could enable attackers to access confidential business information.
• System Integrity Compromise: Attackers could modify critical configurations or interfere with system operations.
• Operational Disruption: Successful exploitation could affect system availability and interrupt business services.
• Security Control Bypass: Privilege escalation could allow attackers to perform activities that would otherwise be restricted.

The greatest concern is that an attacker who already has limited access could potentially turn that foothold into significantly broader system control.

“A low-privilege account should never become a gateway to SYSTEM-level control. This vulnerability creates that risk.”

Workaround

No official mitigations or workarounds are documented for this vulnerability.

An official fix is identified, but the specific fixed build and associated KB article are not confirmed.

Until the fix can be applied, organizations should consider restricting local access, limiting privileged accounts, and monitoring suspicious privilege escalation activity.

These measures may help reduce exposure but are not confirmed substitutes for the security fix.

Urgency

CVE-2026-62840 is rated Critical, with a CVSS base score of 7.0, and should be prioritized for security remediation.

Although active exploitation has not been reported and exploitation is considered less likely, the vulnerability could allow an attacker with limited privileges to obtain SYSTEM-level access.

The combination of high confidentiality, integrity, and availability impacts makes successful exploitation potentially damaging to business operations.

Organizations should identify affected systems running the Microsoft MANA Network Driver and prioritize deployment of the official security fix.

The absence of confirmed exploitation should not be interpreted as the absence of risk.