CVE-2026-19811
Deferred Deferred - Pending Action

Stack-Based Buffer Overflow in TOTOLINK A800R Router

Publication date: 2026-08-14

Last updated on: 2026-08-14

Assigner: VulDB

Description
A security flaw has been discovered in TOTOLINK A800R 4.1.2cu.5137_B20200730. The impacted element is the function setIpQosRules of the file /cgi-bin/cstecgi.cgi of the component firewall.so. The manipulation of the argument Comment results in stack-based buffer overflow. The attack can be executed remotely. The exploit has been released to the public and may be used for attacks.

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Meta Information

Published
2026-08-14
Last Modified
2026-08-14
Generated
2026-08-15
AI Q&A
2026-08-14
EPSS Evaluated
2026-08-14
NVD
CVE-2026-19811
EUVD
EUVD-2026-58599

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
totolink a800r 4.1.2cu.5137_b20200730

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-121 A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).
CWE-119 The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

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Executive Summary

This is a stack-based buffer overflow vulnerability in the TOTOLINK A800R router firmware version V4.1.2cu.5137_B20200730. The flaw exists in the setIpQosRules function of the firewall.so component. The function takes the 'Comment' parameter from user requests and passes it directly to strcpy without bounds checking, allowing an attacker to overflow the stack by sending a maliciously crafted HTTP POST request with an excessively long 'comment' value.

Detection Guidance

To detect this vulnerability, check if your TOTOLINK A800R router is running firmware version V4.1.2cu.5137_B20200730. You can verify this by logging into the router's admin panel and checking the firmware version in the system settings. Additionally, monitor network traffic for HTTP POST requests to /cgi-bin/cstecgi.cgi with unusually long 'comment' parameters.

Impact Analysis

An attacker could exploit this vulnerability to execute arbitrary code on the affected router remotely. This could lead to unauthorized access, data theft, or disruption of network services. Since the exploit is publicly available, the risk of widespread attacks is higher.

Compliance Impact

This vulnerability could potentially impact compliance with GDPR and HIPAA by enabling unauthorized remote access to a network device. A stack-based buffer overflow in the TOTOLINK A800R router may allow attackers to execute arbitrary code, leading to data breaches or unauthorized system access. Such breaches could violate GDPR's data protection requirements or HIPAA's safeguards for protected health information if exploited.

Mitigation Strategies

Immediately update the router's firmware to the latest version provided by TOTOLINK. If no update is available, disable remote access to the router's web interface and block external HTTP POST requests to /cgi-bin/cstecgi.cgi. Consider replacing the device if the vendor does not provide a patch.

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