CVE-2023-4623 represents a critical use-after-free vulnerability located within the Linux kernel's net/sched: sch_hfsc (HFSC qdisc traffic control) component. This vulnerability allows an attacker to exploit the flaw to achieve local privilege escalation. The severity level is classified as high, with a CVSS score of 7.8, indicating that this flaw poses a significant risk to organizations. The vulnerability was published on September 6, 2023, and organizations are urged to act swiftly to mitigate potential risks.
The exploitation status for this vulnerability indicates that no public exploit or proof of concept has been confirmed as of now. Nonetheless, organizations must prioritize patching immediately, given the potential for local privilege escalation. The nature of this vulnerability calls for immediate attention from security teams to assess their systems and ensure they are not vulnerable.
Analyzing the risk context, organizations utilizing affected versions of the Debian Linux kernel should be particularly vigilant. The exposure from this vulnerability could lead to unauthorized access and control over systems, which is a critical concern for maintaining system integrity and security.
Defenders are advised to review their systems for the presence of this vulnerability, especially if they are operating versions of the Linux kernel specified in the advisory. Compliance with patching timelines and regular security assessments will bolster defenses against such vulnerabilities.
Vulnerability Details
The official description of CVE-2023-4623 states that a use-after-free vulnerability in the Linux kernel's net/sched: sch_hfsc component can be exploited to achieve local privilege escalation. If a class with a link-sharing curve is present, and its parent lacks a link-sharing curve, a dangling pointer may result from a failure to remove it in certain function calls, leading to the potential for exploitation.
This vulnerability is classified under CWE-416, indicating a use-after-free condition. The CVSS vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, resulting in a base score of 7.8, reflecting its high severity. The affected vendor is both Debian and Linux, with specific configurations of the Linux kernel identified as vulnerable.
Organizations are advised to upgrade past commit b3d26c5702c7d6c45456326e56d2ccf3f103e60f to mitigate this vulnerability.
Technical Analysis
The root cause of CVE-2023-4623 lies in how the Linux kernel handles link-sharing curves within its traffic control mechanisms. Specifically, when a class with the HFSC_FSC flag set has a parent that lacks a link-sharing curve, it results in improper memory management. The init_vf() function calls vttree_insert() on the parent, while the corresponding vttree_remove() call is skipped during update_vf(). This oversight creates a dangling pointer that can trigger a use-after-free condition.
The attack vector for this vulnerability is local, meaning an attacker must have local access to the system to exploit it. The complexity of the attack is low, requiring minimal effort to exploit the vulnerability once access is gained. The privileges required for successful exploitation are low, as local users can leverage this flaw without needing elevated permissions.
User interaction is not required for this vulnerability, meaning it can be exploited autonomously by an attacker once they have local access. The impacts of successful exploitation are severe, affecting confidentiality, integrity, and availability. These impacts can result in unauthorized access, data manipulation, and potential system outages.
Risk & Impact Analysis
The potential risks associated with CVE-2023-4623 are substantial, particularly for organizations that rely on the affected versions of the Linux kernel. Risk to organizations includes unauthorized access to sensitive systems and data, which can lead to severe operational disruptions and compromise of confidential information.
The blast radius of this vulnerability is significant, as it can impact any local user who is able to exploit the flaw. The urgency for organizations to address this vulnerability is high, as indicated by its CVSS score of 7.8. Organizations should prioritize patching immediately to safeguard against exploitation.
In light of the exploitation status, with no public exploit confirmed, the window of opportunity remains limited. However, given the nature of the vulnerability and its potential impact, proactive measures should be taken as a precaution.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The affected versions of the Linux kernel include all versions from 2.6.12 up to 4.14.327, from 4.15 to 4.19.295, from 4.20 to 5.4.257, from 5.5 to 5.10.195, from 5.11 to 5.15.132, from 5.16 to 6.1.53, and from 6.2 to 6.4.16. Additionally, Debian Linux version 10.0 is also affected.
Mitigation & Remediation
Organizations should upgrade their systems past commit b3d26c5702c7d6c45456326e56d2ccf3f103e60f to remediate this vulnerability. If immediate patching is not feasible, consider implementing network segmentation to limit access to vulnerable systems while remediation efforts are underway.
For those unable to patch immediately, applying configuration hardening and restricting access to the systems can help mitigate potential risks. Continuous monitoring for any suspicious activity should also be conducted as part of a proactive security posture.
Organizations should prioritize patching immediately to prevent unauthorized access through this vulnerability.
Detection Guidance
Monitoring system logs for unusual access patterns or attempts to exploit local vulnerabilities can help identify potential exploitation. Additionally, tracking changes in system configurations or unauthorized installations can provide insights into malicious activities.
Organizations are encouraged to maintain an inventory of their systems and regularly assess them for compliance with security best practices.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2023-4623 highlights the importance of robust memory management within critical components of operating systems. This vulnerability showcases common pitfalls in kernel development, reiterating the necessity for thorough code reviews and security assessments.
Security teams should take this opportunity to reevaluate their security practices, ensuring that vulnerabilities are identified and patched promptly. The patterns observed in this and similar vulnerabilities demonstrate the evolving threat landscape, which necessitates continuous adaptation of security measures.
For comprehensive security strategies, organizations may consider leveraging services such as penetration testing and regular vulnerability assessments to enhance their defenses.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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