In the Linux kernel, a high-severity vulnerability has been identified that allows for out-of-bound memory access. This issue arises during the execution of an ioctl FBIOPUT_VSCREENINFO command, where a userspace program passes an incomplete fb_var_screeninfo struct. The incomplete struct can lead to incorrect calculations during screen updates, potentially allowing unauthorized access to memory locations.
The CVSS score for this vulnerability is 7.1, indicating a high severity level. The attack vector is classified as local, requiring low complexity and low privileges for exploitation. Given the potential for high confidentiality and availability impact, it is crucial that organizations address this vulnerability promptly.
Organizations should prioritize patching immediately. The vulnerability has been documented with CVE ID CVE-2021-47383, and it is critical to stay informed about updates and patches provided by the Linux kernel maintainers.
Monitoring for any exploit attempts related to this vulnerability is also necessary, as it could pose significant risks to systems utilizing affected versions of the Linux kernel.
Vulnerability Details
In the Linux kernel, the following vulnerability has been resolved: tty: Fix out-of-bound vmalloc access in imageblit This issue happens when a userspace program does an ioctl FBIOPUT_VSCREENINFO passing the fb_var_screeninfo struct containing only the fields xres, yres, and bits_per_pixel with values. If this struct is the same as the previous ioctl, the vc_resize() detects it and doesn't call the resize_screen(), leaving the fb_var_screeninfo incomplete. This leads to the updatescrollmode() calculating a wrong value to fbcon_display->vrows, which makes the real_y() return a wrong value of y, and that value, eventually, causes the imageblit to access an out-of-bound address value. To solve this issue, the resize_screen() is called even if the screen does not need any resizing, so it will 'fix and fill' the fb_var_screeninfo independently.
The vulnerability is classified under CWE-125, which pertains to out-of-bounds read.
Technical Analysis
The root cause of this vulnerability lies in the handling of the fb_var_screeninfo struct during ioctl calls. Specifically, when the struct does not change between calls, the system fails to properly update the necessary fields, leading to incorrect memory access. The attack vector is local, meaning that an attacker would need access to the local system to exploit this vulnerability. The attack complexity is low, as it does not require advanced skills or resources. Additionally, only low privileges are needed to exploit this vulnerability, and user interaction is not required.
The impacts of this vulnerability include high confidentiality and high availability impact, as attackers may gain unauthorized access to sensitive data or disrupt service.
Risk & Impact Analysis
The real-world risk associated with this vulnerability includes potential data breaches and service interruptions, which could lead to significant operational disruption. Given the nature of the vulnerability, its exploitation could affect numerous systems running vulnerable versions of the Linux kernel.
The urgency for organizations to address this vulnerability is high. Organizations should assess their systems to determine if they are running affected versions and prioritize patching as part of their security strategy.
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The vulnerability affects Linux kernel versions prior to 4.4.286, as well as versions from 4.5 to 4.9.285, 4.10 to 4.14.249, 4.15 to 4.19.209, 4.20 to 5.4.151, 5.5 to 5.10.71, and 5.11 to 5.14.10.
Mitigation & Remediation
Organizations should apply the latest patches provided by the Linux kernel maintainers to mitigate this vulnerability. The patches address the out-of-bounds access issue and ensure that the fb_var_screeninfo struct is correctly updated, reducing the potential for exploitation.
If immediate patching is not possible, organizations should consider implementing workarounds, such as restricting access to the affected functionality or monitoring for unusual activity that may indicate exploitation attempts.
Configuration hardening should also be part of the remediation strategy, ensuring that systems are secured against potential exploits.
For further assistance, organizations may consider engaging in penetration testing services to identify vulnerabilities and enhance their security posture.
Detection Guidance
To detect potential exploitation of this vulnerability, organizations should monitor logs for unusual ioctl calls that may indicate attempts to exploit the out-of-bounds access. Additionally, behavioral anomalies in userspace applications interacting with the Linux kernel should be noted.
Network signatures for potential exploit attempts should also be established to provide early detection and response capabilities.
AppSecure Threat Intelligence Insight
This vulnerability highlights the ongoing need for robust security practices within the Linux kernel ecosystem. Continuous monitoring and timely updates are essential for maintaining security integrity. The historical context of similar vulnerabilities underscores the importance of proactive security measures.
Organizations should develop a comprehensive strategy for vulnerability management that includes regular assessments and timely patching to mitigate risks effectively. Further insights can be gained from resources such as the vulnerability management program and the importance of proactive security measures.
Engaging in thorough security testing, including penetration testing methodology, can further enhance an organization's security posture.
As threats evolve, organizations must remain vigilant and adaptable in their security strategies to effectively counter emerging risks.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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