CVE-2021-47548

Comprehensive Technical Analysis of CVE-2021-47548

1. Vulnerability Assessment and Severity Evaluation

CVE ID: CVE-2021-47548

CVSS Score: 9.8

Severity: Critical

Description: The vulnerability involves an array overflow in the hns_dsaf_ge_srst_by_port() function within the Linux kernel's Ethernet driver for Hisilicon hardware. Specifically, the issue arises when the port variable is set to 6 or 7, leading to an out-of-bounds access in the dsaf_dev->mac_cb array, which has a length of DSAF_MAX_PORT_NUM (i.e., 6). This can result in undefined behavior, including potential memory corruption and system crashes.

Impact:

• Confidentiality: High
• Integrity: High
• Availability: High

The high CVSS score indicates that this vulnerability can be exploited to cause significant damage, including unauthorized access, data corruption, and denial of service.

2. Potential Attack Vectors and Exploitation Methods

Attack Vectors:

• Local Exploitation: An attacker with local access to the system could manipulate the port variable to trigger the array overflow.
• Remote Exploitation: If the vulnerable function can be triggered remotely (e.g., through network packets), an attacker could exploit this vulnerability over the network.

Exploitation Methods:

• Memory Corruption: By carefully crafting input to set the port variable to 6 or 7, an attacker could cause memory corruption, leading to arbitrary code execution or system crashes.
• Denial of Service (DoS): An attacker could exploit this vulnerability to cause the system to crash, resulting in a DoS condition.

3. Affected Systems and Software Versions

Affected Systems:

• Systems running the Linux kernel with the Hisilicon Ethernet driver (hns).

Affected Software Versions:

• Specific versions of the Linux kernel that include the vulnerable hns_dsaf_ge_srst_by_port() function. The exact versions can be identified by reviewing the patch references provided.

4. Recommended Mitigation Strategies

Immediate Actions:

• Apply Patches: Ensure that the system is updated with the latest kernel patches that address this vulnerability. Relevant patches can be found in the provided references.
• Restrict Access: Limit local and remote access to the system to trusted users only.

Long-Term Strategies:

• Regular Updates: Implement a robust patch management process to ensure timely updates and patches.
• Monitoring: Use intrusion detection systems (IDS) and intrusion prevention systems (IPS) to monitor for suspicious activities that may indicate an attempt to exploit this vulnerability.
• Code Review: Conduct thorough code reviews and static analysis to identify and fix similar issues in other parts of the codebase.

5. Impact on Cybersecurity Landscape

Immediate Impact:

• System Stability: Systems running the vulnerable kernel version are at risk of crashes and potential data corruption.
• Security Risks: Exploitation of this vulnerability can lead to unauthorized access and data breaches.

Long-Term Impact:

• Increased Awareness: This vulnerability highlights the importance of thorough code reviews and the need for robust security measures in kernel development.
• Patch Management: Emphasizes the critical role of timely patching and updating systems to mitigate known vulnerabilities.

6. Technical Details for Security Professionals

Vulnerable Code:

if (port >= DSAF_GE_NUM)
    return;

port_rst_off = dsaf_dev->mac_cb[port]->port_rst_off;

Issue:

• The port variable is checked against DSAF_GE_NUM (i.e., 8), but the array dsaf_dev->mac_cb has a length of DSAF_MAX_PORT_NUM (i.e., 6). This discrepancy allows for out-of-bounds access when port is 6 or 7.

Fix:

• Add an additional check to ensure port is less than DSAF_MAX_PORT_NUM before accessing the array.

if (port >= DSAF_MAX_PORT_NUM)
    return;

port_rst_off = dsaf_dev->mac_cb[port]->port_rst_off;

References:

• Patch 1
• Patch 2
• Patch 3
• Patch 4
• Patch 5
• Patch 6
• Patch 7

By addressing this vulnerability promptly and implementing robust security measures, organizations can mitigate the risks associated with CVE-2021-47548 and enhance their overall cybersecurity posture.