CVE-2021-28840 in DAP-2310
Summary
by MITRE • 08/11/2021
Null Pointer Dereference vulnerability exists in D-Link DAP-2310 2.07.RC031, DAP-2330 1.07.RC028, DAP-2360 2.07.RC043, DAP-2553 3.06.RC027, DAP-2660 1.13.RC074, DAP-2690 3.16.RC100, DAP-2695 1.17.RC063, DAP-3320 1.01.RC014 and DAP-3662 1.01.RC022 in the upload_config function of sbin/httpd binary. When the binary handle the specific HTTP GET request, the content in upload_file variable is NULL in the upload_config function then the strncasecmp would take NULL as first argument, and incur the NULL pointer dereference vulnerability.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 08/16/2021
The vulnerability described in CVE-2021-28840 represents a critical null pointer dereference flaw within the D-Link DAP series wireless access points, specifically affecting models including DAP-2310, DAP-2330, DAP-2360, DAP-2553, DAP-2660, DAP-2690, DAP-2695, DAP-3320, and DAP-3662. This issue resides in the sbin/httpd binary's upload_config function, which processes HTTP GET requests for configuration uploads. The vulnerability manifests when the system handles specific HTTP requests where the upload_file variable contains a null value, leading to a dangerous condition where the strncasecmp function receives a null pointer as its first argument. This fundamental flaw in input validation and memory management creates a path for potential system crashes or unauthorized access scenarios that could compromise the device's operational integrity.
The technical implementation of this vulnerability stems from improper handling of user-supplied input within the HTTP request processing pipeline. When an attacker crafts a specific HTTP GET request, the system's parsing logic fails to adequately validate the upload_file variable before passing it to the strncasecmp function. This function, designed to perform case-insensitive string comparisons, becomes vulnerable to a null pointer dereference when it receives a null value as its first parameter. The underlying issue demonstrates poor defensive programming practices and inadequate input sanitization mechanisms. According to CWE-476, this vulnerability directly maps to a null pointer dereference condition where a null value is passed to a function that expects a valid pointer, creating a potential for system instability or complete service disruption.
The operational impact of this vulnerability extends beyond simple system crashes, as it represents a potential entry point for more sophisticated attacks within the context of the ATT&CK framework's initial access and execution phases. An attacker could exploit this vulnerability to cause denial of service conditions, potentially disrupting network connectivity for wireless clients connected to these access points. The vulnerability's exploitation could lead to persistent service interruptions that affect business operations and network availability. Furthermore, the null pointer dereference could potentially be leveraged as a stepping stone for additional attacks, particularly in environments where these devices are not properly segmented or monitored. The vulnerability affects multiple D-Link models across different firmware versions, indicating a systemic issue within the software architecture that requires comprehensive remediation across the affected product line.
Mitigation strategies for this vulnerability should focus on implementing proper input validation and null pointer checks within the affected software components. Organizations should immediately apply firmware updates provided by D-Link to address this specific null pointer dereference issue. Network administrators should also implement monitoring solutions to detect anomalous HTTP request patterns that might indicate exploitation attempts. The vulnerability highlights the importance of secure coding practices and defensive programming techniques, particularly around pointer validation and input sanitization. Regular security assessments of network infrastructure components should include checks for similar null pointer dereference conditions, as this represents a common class of vulnerabilities that can lead to significant operational disruptions and potential security breaches. Additionally, implementing network segmentation and access controls around these devices can help limit the potential impact if exploitation occurs.