CVE-2022-29581 in Linux
Summary
by MITRE • 05/17/2022
Improper Update of Reference Count vulnerability in net/sched of Linux Kernel allows local attacker to cause privilege escalation to root. This issue affects: Linux Kernel versions prior to 5.18; version 4.14 and later versions.
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Analysis
by VulDB Data Team • 11/23/2025
The vulnerability identified as CVE-2022-29581 represents a critical improper update of reference count flaw within the Linux kernel's networking subsystem, specifically in the net/sched component. This issue manifests as a privilege escalation vulnerability that enables local attackers to gain root privileges on affected systems. The vulnerability stems from inadequate handling of reference counting mechanisms when managing network scheduling objects, creating a scenario where malicious code can manipulate kernel data structures through improper reference count updates. The flaw exists in the kernel's traffic control subsystem, which is responsible for managing network packet scheduling and queuing disciplines. Attackers exploiting this vulnerability can leverage the reference count manipulation to trigger use-after-free conditions or other memory corruption scenarios that ultimately lead to privilege escalation. This vulnerability affects a broad range of Linux kernel versions, particularly those prior to 5.18, with additional impact on version 4.14 and later versions, indicating a long-standing issue that has persisted across multiple kernel release lines.
The technical implementation of this vulnerability involves the manipulation of reference counters associated with network scheduling objects within the kernel's networking stack. When network queuing disciplines or traffic control objects are created, modified, or destroyed, the kernel maintains reference counts to track object usage and ensure proper memory management. The flaw occurs when these reference counts are not properly updated during specific operations, allowing an attacker to cause objects to be freed prematurely while still being referenced, or to prevent proper cleanup of objects that should be removed. This improper reference count management creates opportunities for attackers to exploit memory layout vulnerabilities, potentially leading to code execution with kernel privileges. The vulnerability is particularly dangerous because it operates at the kernel level where any privilege escalation directly translates to full system compromise. The reference counting issue typically manifests when multiple threads or processes interact with network scheduling objects concurrently, creating race conditions or improper state transitions that corrupt the reference count values.
The operational impact of CVE-2022-29581 extends beyond simple privilege escalation to encompass complete system compromise and potential data exfiltration capabilities. Local attackers who can execute code on a target system can leverage this vulnerability to gain root access without requiring physical access or specialized hardware. Once escalated to root privileges, attackers can modify system files, install persistent backdoors, monitor network traffic, access all user data, and potentially compromise other systems on the network. The vulnerability's presence in both older kernel versions and more recent releases means that organizations running various Linux distributions and kernel versions may be at risk. The attack surface includes any system where network scheduling is actively used, which encompasses virtually all modern Linux systems, particularly servers, routers, and networked devices. The exploitation typically requires local access to the system, making it a significant concern for environments where privilege separation is not properly enforced, and for systems where local users might have access to potentially vulnerable kernel interfaces.
Mitigation strategies for CVE-2022-29581 focus primarily on kernel version updates and system hardening measures. The most effective immediate solution involves upgrading to Linux kernel versions 5.18 or later, where the reference counting implementation has been corrected. Organizations should prioritize patching affected systems and conducting thorough vulnerability assessments to identify systems running vulnerable kernel versions. Additional mitigations include implementing proper privilege separation, limiting local user access to network configuration interfaces, and monitoring for unusual network scheduling activities that might indicate exploitation attempts. System administrators should also consider implementing kernel lockdown mechanisms and disabling unnecessary network scheduling features when not required. The vulnerability aligns with CWE-476 which addresses null pointer dereference issues, and can be mapped to ATT&CK technique T1068 which covers local privilege escalation. Organizations should also implement network monitoring to detect potential exploitation attempts and establish incident response procedures specifically addressing kernel-level privilege escalation vulnerabilities. Regular security assessments and kernel update policies are essential for maintaining system security posture against such persistent kernel-level vulnerabilities.