CVE-2022-40868 is a critical stack overflow vulnerability identified in the Tenda W20E router firmware version V15.11.0.6 (specifically US_W20EV4.0br_V15.11.0.6(1068_1546_841)_CN_TDC). The vulnerability exists in the function formDelDhcpRule, which processes requests sent to the /goform/delDhcpRules/ endpoint. A stack overflow occurs when this function improperly handles input data, allowing an attacker to overwrite parts of the stack memory. This can lead to arbitrary code execution, denial of service, or other malicious outcomes. The vulnerability is remotely exploitable over the network without requiring authentication or user interaction, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N). The severity is rated critical with a CVSS score of 9.8, reflecting high impact on confidentiality, integrity, and availability. The vulnerability is classified under CWE-787 (Out-of-bounds Write), a common and dangerous software weakness. No patches or fixes have been publicly linked yet, and no known exploits in the wild have been reported as of the publication date. However, the ease of exploitation and critical impact make this a significant threat to any organization using the affected router model and firmware version.

For European organizations, the exploitation of CVE-2022-40868 could have severe consequences. Compromised routers can serve as entry points into internal networks, allowing attackers to intercept, modify, or redirect traffic, leading to data breaches or espionage. The ability to execute arbitrary code remotely without authentication means attackers could deploy malware, establish persistent backdoors, or disrupt network availability. This is particularly concerning for enterprises relying on Tenda W20E routers for critical communications or in remote office setups. The impact extends to confidentiality (data interception), integrity (traffic manipulation), and availability (denial of service). Additionally, compromised routers could be leveraged in botnets or for launching further attacks, amplifying the threat landscape. Given the critical nature of this vulnerability, European organizations must prioritize detection and remediation to prevent potential operational disruptions and data loss.

1. Immediate mitigation involves isolating affected Tenda W20E routers from critical network segments and restricting access to the management interface, especially from untrusted networks. 2. Monitor network traffic for unusual requests targeting the /goform/delDhcpRules/ endpoint or signs of exploitation attempts. 3. Implement network-level protections such as firewall rules to block unauthorized access to router management ports and endpoints. 4. Since no official patches are currently available, consider temporary replacement or firmware rollback to a version not affected if feasible. 5. Engage with Tenda support or authorized vendors to obtain updates or security advisories. 6. Conduct regular vulnerability scans and penetration tests focusing on network infrastructure devices to detect similar vulnerabilities. 7. Educate IT staff on the risks of unmanaged or outdated network devices and enforce strict device management policies. 8. Employ network segmentation to limit the impact of any compromised device and use intrusion detection/prevention systems to identify exploitation attempts.