Linux Kernel Remote Code Execution

Byadmblake

What is the Attack? FortiGuard Labs is monitoring CVE-2026-98432, a critical use-after-free vulnerability in the Linux kernel’s IPv4 networking subsystem that could allow an unauthenticated remote attacker to execute arbitrary code with kernel-level privileges. The vulnerability stems from improper memory management during TCP connection request processing. Under specific conditions, concurrent operations may access socket-option memory…

What is the Attack?

FortiGuard Labs is monitoring CVE-2026-98432, a critical use-after-free vulnerability in the Linux kernel’s IPv4 networking subsystem that could allow an unauthenticated remote attacker to execute arbitrary code with kernel-level privileges.

The vulnerability stems from improper memory management during TCP connection request processing. Under specific conditions, concurrent operations may access socket-option memory after it has been freed, resulting in a use-after-free condition.

An attacker can potentially trigger this flaw by sending specially crafted IPv4 TCP packets containing IP options to a vulnerable system. Exploitation requires precise timing but does not require authentication or user interaction.

Successful exploitation could result in kernel memory corruption, information disclosure, denial of service, or potentially remote code execution with kernel-level privileges.

What is the recommended Mitigation?

The vulnerability was introduced in Linux kernel 4.4. The upstream Linux kernel CVE team has published fixes for multiple supported kernel branches.

Ubuntu confirmed on November 2 that fixes for Ubuntu 22.04 and newer were available in its proposed repository while undergoing qualification testing. Ubuntu 26.10 already includes the fix.

Organizations running potentially affected Linux systems should:

1. Apply security updates: Install the latest kernel security updates provided by the respective Linux distribution.

2. Reboot affected systems: Restart systems after installing the updated kernel to ensure the patched kernel is running.

3. Restrict network exposure: Limit unnecessary inbound TCP connections from untrusted networks.

4. Filter IPv4 packets containing IP options: Red Hat provides an interim nftables rule to reduce exposure to the vulnerable code path.

What FortiGuard Coverage is available?

• FortiGuard Labs continues to monitor CVE-2026-98432, including developments in exploitation research, vendor security updates, and the availability of security patches across affected Linux distributions.

• FortiGuard Labs will provide additional updates as new intelligence and protections become available.

• FortiGate Intrusion Prevention System (IPS): Provides network-level intrusion prevention and detection against known exploitation attempts targeting CVE-2026-98432.

Intrusion Prevention | FortiGuard Labs

• FortiGuard Labs has released Endpoint Vulnerability signatures to identify vulnerable Linux kernel components across your network, helping organizations detect potentially affected systems and prioritize remediation.

FortiGuard Labs

• FortiGuard Incident Response supports investigation, containment, and recovery following suspected compromise of Linux distributions.

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