CVE-2023-4921 is a high-severity use-after-free vulnerability affecting the Linux kernel's net/sched: sch_qfq component. This vulnerability allows attackers with local access to escalate their privileges, potentially leading to unauthorized access or control over the system. The CVSS score of 7.8 indicates a significant risk, as the vulnerability can result in high impacts on confidentiality, integrity, and availability.
The vulnerability arises when the plug qdisc is used as a class of the qfq qdisc. Specifically, sending network packets can trigger a use-after-free condition in the qfq_dequeue() function due to an incorrect .peek handler of sch_plug and a lack of error checking in agg_dequeue(). This flaw can be exploited by local users to gain elevated privileges.
Organizations should prioritize patching immediately. Users are advised to upgrade their systems to versions beyond the specified commit (8fc134fee27f2263988ae38920bc03da416b03d8) to mitigate the risks associated with this vulnerability.
The vulnerability was published on September 12, 2023, and it is essential for organizations to remain vigilant in monitoring their systems for any potential exploitation attempts. The ongoing risk necessitates swift action to secure affected systems.
Vulnerability Details
The official description of CVE-2023-4921 indicates that it is a use-after-free vulnerability in the Linux kernel's net/sched: sch_qfq component. According to the CVSS version 3.1 metrics, it has a base score of 7.8, classified as high severity. The vulnerability has a local attack vector, low complexity, and requires low privileges with no user interaction.
The impacts of this vulnerability are severe, affecting confidentiality, integrity, and availability, all rated as high. The specific component affected is the Linux kernel, and the vulnerability has been assigned CWE-416.
Technical Analysis
The root cause of CVE-2023-4921 is a use-after-free condition that occurs in the qfq_dequeue() function. This happens when the incorrect .peek handler of sch_plug is used, resulting in a lack of error checking in the agg_dequeue() function. The attack vector is local, meaning that an attacker must have access to the system.
The attack complexity is low, with attackers requiring only low privileges to exploit the vulnerability. Importantly, no user interaction is required for exploitation. The confidentiality, integrity, and availability impacts are all rated as high, indicating that successful exploitation can lead to severe consequences for the affected systems.
Risk & Impact Analysis
Organizations utilizing the affected versions of the Linux kernel face significant risks due to this vulnerability. The potential for local privilege escalation means that attackers could gain unauthorized access to sensitive information or control over critical system functions.
The blast radius is considerable, as the vulnerability affects multiple versions of the Linux kernel and Debian systems. Swift action is necessary to mitigate the risk associated with this vulnerability and to protect organizational assets.
Given the CVSS score of 7.8, organizations should address this vulnerability in their priority patch cycle. The urgency is heightened by the potential impact it could have on system security and operational integrity.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The following versions of the Linux kernel and Debian Linux are affected by CVE-2023-4921: - All versions prior to patch version 4.14.326 - All versions prior to patch version 4.19.295 - All versions prior to patch version 5.4.257 - All versions prior to patch version 5.10.195 - All versions prior to patch version 5.15.132 - All versions prior to patch version 6.1.54 - All versions prior to patch version 6.5.4 - Debian Linux 10.0.
Mitigation & Remediation
To mitigate the risks associated with CVE-2023-4921, organizations should upgrade their Linux kernel to versions beyond the specified commit (8fc134fee27f2263988ae38920bc03da416b03d8). If an immediate upgrade is not possible, implementing configuration hardening and network controls can help to reduce exposure.
Monitoring for unusual system behavior and applying security patches promptly are critical in maintaining a secure environment. Organizations should also consider conducting regular penetration testing to identify and remediate vulnerabilities.
For further information on effective security practices, organizations can refer to the penetration testing services that help validate remediation.
Detection Guidance
Organizations should monitor their systems for indicators of exploitation related to CVE-2023-4921. Key indicators include log entries related to abnormal network activity, attempts to access restricted resources, and unexpected system changes.
Behavioral anomalies such as sudden spikes in user privileges or unauthorized access attempts should also be closely watched. Implementing network signatures that can detect exploit attempts is recommended.
AppSecure Threat Intelligence Insight
CVE-2023-4921 represents a significant vulnerability that highlights the ongoing challenges associated with memory management in kernel-level components. The use-after-free vulnerability underscores the need for ongoing security assessments and updates in the software development lifecycle.
Security teams should take this incident as a lesson to implement robust testing and validation strategies within their development processes. Regular vulnerability assessments, such as those provided by vulnerability management programs, are essential to maintaining a secure environment.
Additionally, organizations should consider leveraging penetration testing methodologies to identify and remediate similar vulnerabilities proactively.
Emphasizing a culture of security awareness and continuous improvement can help organizations stay ahead of emerging threats.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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