In the Linux kernel, a vulnerability has been resolved that can lead to a local denial of service. This issue arises from a NULL pointer dereference when deactivating inactive aggregates during the qfq_reset process. The vulnerability is classified as medium severity with a CVSS score of 5.5, indicating a moderate risk to systems.
The vulnerability allows attackers with local access to exploit the behavior of the QFQ queuing discipline, leading to potential system crashes. Organizations should be aware of the risks this vulnerability poses, particularly in environments where the Linux kernel is deployed. The urgency for defenders is high, and immediate patching is recommended to prevent exploitation.
The Linux kernel’s vulnerability has been published on January 21, 2026, and patched in subsequent releases. The attack vector is local, requiring low privileges, and no user interaction is necessary for exploitation.
Organizations should prioritize patching immediately to mitigate potential risks associated with this vulnerability.
Vulnerability Details
In the Linux kernel, the vulnerability allows for a NULL dereference when deactivating inactive aggregates in the QFQ scheduler. The issue occurs because two qfq_class objects may reference the same leaf_qdisc, leading to a situation where the class is incorrectly deactivated.
The CVSS score is 5.5, classified as medium severity. The potential impacts include high availability impact, with confidentiality and integrity impacts rated as none. The vulnerability affects the Linux kernel versions from 3.0 to below 5.10.248, 5.11 to below 5.15.198, 5.16 to below 6.1.161, 6.2 to below 6.6.121, and various release candidates of 6.19.
Technical Analysis
The root cause of this vulnerability lies in the way the QFQ queuing discipline manages references to its classes and leaf_qdiscs. When a QFQ qdisc is attached and another is referenced temporarily, it can lead to the deactivation of an inactive aggregate, ultimately causing a NULL pointer dereference.
The attack vector is local, and the complexity is low, requiring only that the attacker has low privileges to trigger the NULL dereference. No user interaction is needed, making it easier for attackers to exploit this vulnerability. The impact on availability is high due to the potential system crash.
Risk & Impact Analysis
The real-world risk of this vulnerability is significant, particularly for systems running older versions of the Linux kernel. Organizations that fail to patch may experience service interruptions or degraded performance, impacting their operational capabilities.
The blast radius potential is considerable, as the vulnerability affects multiple kernel versions. Given the low privileges required for exploitation, this vulnerability can be leveraged by local users or attackers with access to the system.
Organizations should address this vulnerability in their patch cycle urgently due to its medium severity rating and the potential for high availability impact.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The vulnerability affects all versions of the Linux kernel prior to the vendor's patch, specifically versions from 3.0 to below 5.10.248, from 5.11 to below 5.15.198, from 5.16 to below 6.1.161, and from 6.2 to below 6.6.121.
Mitigation & Remediation
Organizations should apply the latest patches to their Linux kernel installations to mitigate this vulnerability. If patches are not immediately available, consider implementing workarounds such as restricting access to the kernel or disabling the affected QFQ qdisc until a patch can be applied.
For additional security assurance, organizations can engage in penetration testing to identify any remaining vulnerabilities in their systems.
Detection Guidance
To detect potential exploitation of this vulnerability, organizations should monitor system logs for NULL pointer dereference messages. Behavioral anomalies that suggest abnormal kernel behavior should also be investigated closely.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2026-22976 highlights the ongoing challenges in kernel security. As kernel vulnerabilities remain a key target for attackers, organizations must maintain robust vulnerability management practices to identify and remediate these issues proactively.
This vulnerability reflects a broader trend of complexity in kernel-level management, where shared resources can lead to unexpected behaviors. Security teams should regularly review their kernel configurations and consider implementing tools that can help detect such vulnerabilities.
Organizations are encouraged to adopt a comprehensive security posture that includes regular penetration testing methodology and incident response strategies to effectively manage vulnerabilities like this.
Additionally, businesses should evaluate their use of kernel features and consider vulnerability management programs that can help mitigate risks associated with kernel vulnerabilities.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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