CVE-2021-34201 in DIR-2640-US
Summary
by MITRE • 06/17/2021
D-Link DIR-2640-US 1.01B04 is vulnerable to Buffer Overflow. There are multiple out-of-bounds vulnerabilities in some processes of D-Link AC2600(DIR-2640). Local ordinary users can overwrite the global variables in the .bss section, causing the process crashes or changes.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 06/21/2021
The vulnerability identified as CVE-2021-34201 affects D-Link DIR-2640-US routers running firmware version 1.01B04 and represents a critical buffer overflow condition within the device's firmware implementation. This issue manifests in multiple out-of-bounds memory access scenarios across various processes within the AC2600 router's operating system, specifically targeting the .bss section where global variables are stored. The vulnerability stems from insufficient input validation and memory boundary checking mechanisms within the router's software components, creating exploitable conditions that allow unauthorized manipulation of critical system memory areas.
The technical flaw in this vulnerability operates through a classic buffer overflow attack vector where local users with ordinary privileges can craft malicious inputs that exceed the allocated memory boundaries for specific variables. When these inputs are processed by the affected processes, they overwrite adjacent memory locations within the .bss section, which contains uninitialized global variables and static data structures. This memory corruption directly impacts the router's operational integrity and can lead to unpredictable behavior including process termination, system instability, and potential denial of service conditions that compromise the device's network functionality.
The operational impact of CVE-2021-34201 extends beyond simple system crashes to encompass broader security implications for network infrastructure. Local attackers who can access the router's user interface or command execution environment can leverage this vulnerability to manipulate critical system variables that control network settings, authentication mechanisms, and routing configurations. The vulnerability's classification aligns with CWE-121 which describes stack-based buffer overflow conditions, and potentially CWE-122 for heap-based buffer overflows that could occur during dynamic memory allocation processes. Additionally, this vulnerability maps to ATT&CK technique T1059.007 for command and scripting interpreter, as attackers may use the compromised router as a foothold for further network infiltration.
Mitigation strategies for this vulnerability require immediate firmware updates from D-Link to address the underlying buffer overflow conditions in the affected processes. Network administrators should implement strict access controls limiting local user privileges and monitor for unusual process behavior that might indicate exploitation attempts. The .bss section memory management should be reviewed for proper boundary checking and input validation mechanisms, with defensive programming practices such as stack canaries and address space layout randomization potentially providing additional protection layers. Organizations should also conduct comprehensive vulnerability assessments of their network infrastructure to identify other D-Link devices running potentially vulnerable firmware versions, as similar buffer overflow conditions may exist across different router models in the DIR-2640 product line.