CVE-2021-33909 is a high-severity vulnerability present in the Linux kernel, specifically affecting versions from 3.16 through 5.13.x prior to 5.13.4. This vulnerability allows an unprivileged user to escalate their privileges to root by exploiting improper restrictions on seq buffer allocations within the kernel's filesystem layer.
The vulnerability is classified with a CVSS score of 7.8, indicating a high severity level. The risk to organizations includes potential unauthorized access to critical system resources, which can lead to further exploitation and compromise of sensitive data.
Organizations should prioritize patching immediately, as the vulnerability poses a significant risk, especially in environments where the kernel is widely deployed. The initial publication date of this CVE was July 20, 2021, and it has since been modified, reflecting ongoing developments and insights into its impact.
The current status indicates that there is a known exploit available, which raises the urgency for organizations to apply the necessary patches to mitigate potential attacks.
In summary, CVE-2021-33909 represents a critical vulnerability within the Linux kernel, necessitating immediate attention and remediation efforts from security teams worldwide.
Vulnerability Details
This vulnerability allows for an integer overflow and an out-of-bounds write due to the improper allocation of seq buffers in the Linux kernel's filesystem. The affected versions include Linux kernel versions 3.16 through 5.13.x prior to 5.13.4.
The CVSS score of 7.8 indicates high severity, highlighting the potential impact on confidentiality, integrity, and availability. An attacker with low privileges can exploit this vulnerability without user interaction, leading to a high impact on the system.
The vulnerability falls under CWE-190 (Integer Overflow or Wraparound) and CWE-787 (Out-of-bounds Write), which are critical weaknesses that can be exploited to gain elevated privileges.
Technical Analysis
The root cause of CVE-2021-33909 stems from a lack of proper checks on seq buffer allocations, allowing an integer overflow. This flaw permits malicious actors to manipulate memory allocations, leading to out-of-bounds writes.
The attack vector for this vulnerability is local, requiring the attacker to have physical or logical access to the system. The attack complexity is low, and privileges required to exploit this vulnerability are minimal (low). Additionally, user interaction is not required.
The impact on confidentiality, integrity, and availability is categorized as high, indicating that successful exploitation could lead to significant damage or compromise of system resources.
Risk & Impact Analysis
Real-world deployment risk for this vulnerability is significant, especially for organizations relying on Linux-based systems. The potential for an unprivileged user to escalate privileges to root can lead to a complete compromise of sensitive data and system integrity.
This matter is critical for organizations, particularly those in sectors that handle sensitive data. The blast radius could extend to any system running affected kernel versions, increasing the urgency for remediation.
Given the CVSS score of 7.8 and the known exploit status, organizations should prioritize patching immediately to mitigate the risks associated with this vulnerability.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | Yes |
Public PoC | Yes |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The following versions of the Linux kernel are affected by this vulnerability: 3.16 through 5.13.x prior to 5.13.4. Additionally, specific distributions such as Debian and Fedora are also impacted.
Mitigation & Remediation
To address this vulnerability, organizations should apply patches provided by their respective Linux distribution vendors. For instance, the patch for Linux kernel version 5.13.4 can be found in the change log at ChangeLog-5.13.4. Organizations that cannot immediately apply the patch should consider implementing workarounds or temporary mitigations while they prepare for the upgrade.
Detection Guidance
Organizations should monitor logs for unusual activities that may indicate exploitation attempts. Key indicators include unexpected system behavior, alterations in file permissions, or unauthorized access attempts.
AppSecure Threat Intelligence Insight
CVE-2021-33909 highlights a critical issue within the Linux kernel that organizations must address proactively. The presence of public proof-of-concept code on GitHub, along with the high exploitability factor, suggests that this vulnerability could be leveraged in real-world attacks.
Security teams should analyze their environments for the presence of affected kernel versions and prioritize applying the relevant patches. This situation serves as a reminder of the importance of maintaining current software versions to mitigate security risks.
For further guidance and resources on vulnerability management and penetration testing, organizations may refer to the vulnerability management program and explore additional penetration testing services to enhance their security posture.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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