CVE-2026-51725 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the NTPSyncWithHost function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to change the device clock via sending a crafted POST request to /cgi-bin/cstecgi.cgi.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 08/31/2026
The vulnerability identified in TOTOLINK T6 router firmware version 4.1.5cu.748_B20211015 represents a critical failure in access control mechanisms within the NTPSyncWithHost function. This flaw allows unauthenticated remote attackers to manipulate the device's system clock by sending crafted HTTP POST requests to the /cgi-bin/cstecgi.cgi endpoint. The root cause lies in the insufficient validation of authentication tokens or session states when processing time synchronization commands, effectively bypassing standard security controls that should restrict such administrative functions to authorized users only.
From a technical perspective, this vulnerability is classified under CWE-284, which describes Improper Access Control. By exploiting this weakness, an attacker can inject arbitrary values into the Network Time Protocol configuration parameters without providing valid credentials. The attack vector involves constructing a specific POST request that targets the cgi script responsible for handling NTP synchronization settings. Since the function does not adequately verify the requester's privileges before executing the clock change operation, it permits unauthorized modification of critical system time variables. This type of flaw is particularly dangerous in embedded networking devices where administrative interfaces are often exposed to untrusted networks or lack robust authentication layers due to design oversights.
The operational impact of this vulnerability extends beyond simple time manipulation. Accurate system time is foundational for the proper functioning of many security protocols and logging mechanisms. An attacker who can alter the device clock may disrupt timestamp-based log entries, rendering forensic analysis difficult or impossible during incident response. Furthermore, incorrect timestamps can cause failures in certificate validation processes that rely on current date checks, potentially allowing man-in-the-middle attacks to succeed if certificates are accepted despite being expired or not yet valid due to manipulated system time. In environments relying on NTP for synchronized operations across multiple devices, this single point of failure could lead to widespread inconsistencies affecting network coordination and data integrity.
This vulnerability aligns with MITRE ATT&CK technique T1076, which involves Time Synchronization Abuse. Adversaries may manipulate local or remote system time to evade detection mechanisms that rely on chronological logs or to disrupt scheduled tasks critical for security monitoring. The ability to change the clock without authentication also facilitates other attacks such as bypassing rate-limiting controls or disrupting session timeouts, thereby extending the attacker's window of opportunity within the network.
Mitigation strategies should prioritize immediate patching if a vendor update is available that addresses this access control flaw. In cases where patches are not yet released, administrators can implement network-level restrictions to limit access to the /cgi-bin/cstecgi.cgi endpoint only from trusted management subnets using firewall rules or ACLs. Additionally, enabling strong authentication mechanisms for all administrative interfaces and disabling unnecessary CGI scripts can reduce the attack surface. Regular security audits focusing on input validation and privilege checks in web-facing functions are essential to prevent similar access control bypasses in embedded systems.