CVE-2023-33673 in AC8
Summary
by MITRE • 06/02/2023
Tenda AC8V4.0-V16.03.34.06 was discovered to contain a stack overflow via the firewallEn parameter in the formSetFirewallCfg function.
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Analysis
by VulDB Data Team • 01/06/2026
The vulnerability identified as CVE-2023-33673 represents a critical stack overflow flaw within the Tenda AC8V4.0-V16.03.34.06 firmware, specifically manifesting through the firewallEn parameter in the formSetFirewallCfg function. This issue resides in the web interface handling of firewall configuration parameters, where insufficient input validation allows malicious actors to craft specially crafted payloads that exceed the allocated stack buffer space. The vulnerability stems from improper bounds checking and string handling mechanisms within the firmware's HTTP request processing module, creating an exploitable condition that can be leveraged by remote attackers without authentication requirements.
The technical implementation of this stack overflow occurs when the firmware processes the firewallEn parameter through the formSetFirewallCfg function, which fails to properly validate the length of user-supplied input before copying it into a fixed-size stack buffer. This classic buffer overflow scenario enables attackers to overwrite adjacent stack memory locations, potentially corrupting program execution flow and allowing for arbitrary code execution. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, which directly relates to improper input validation and inadequate memory management practices. The flaw exists in the firmware's web server component that handles administrative configuration requests, making it accessible through standard HTTP POST requests to the affected device's web interface.
Operationally, this vulnerability presents a significant risk to network security as it allows remote code execution without requiring authentication, effectively granting attackers complete control over the affected router. The attack surface is particularly concerning given that many users operate these devices in residential or small business environments where physical security measures may be minimal. Successful exploitation could enable attackers to establish persistent backdoors, redirect network traffic through malicious proxies, or use the device as a launching point for further attacks against internal networks. The vulnerability's impact aligns with ATT&CK technique T1059.007 for command and script interpreter, as the exploitation would likely involve executing arbitrary commands on the compromised device. Additionally, this flaw could facilitate lateral movement within networks through techniques such as T1021.001 for remote services and T1046 for network service scanning.
Mitigation strategies for CVE-2023-33673 should prioritize immediate firmware updates from Tenda, as the vendor has likely released patches addressing this specific vulnerability. Network administrators should implement network segmentation and access controls to limit exposure of affected devices to untrusted networks. Monitoring for suspicious HTTP traffic patterns and implementing web application firewalls can help detect exploitation attempts. The device should be isolated from critical network segments until proper patching is completed, and security teams should conduct comprehensive network scans to identify all potentially affected devices. Additionally, implementing intrusion detection systems with signature matching for known exploitation patterns can provide early warning of attempted exploitation. Organizations should also consider disabling unnecessary administrative interfaces and implementing strong access controls to minimize the attack surface. Regular vulnerability assessments and firmware update policies should be established to prevent similar issues in future deployments. The vulnerability highlights the importance of secure coding practices and input validation in embedded systems, particularly in network infrastructure devices where security failures can have widespread consequences across entire network environments.