CVE-2026-19812
Received Received - Intake

Stack-Based Buffer Overflow in TOTOLINK A800R

Publication date: 2026-08-14

Last updated on: 2026-08-14

Assigner: VulDB

Description
A weakness has been identified in TOTOLINK A800R 4.1.2cu.5137_B20200730. This affects the function UploadCustomModule of the file /cgi-bin/cstecgi.cgi of the component product.so. This manipulation of the argument File causes stack-based buffer overflow. The attack is possible to be carried out remotely. The exploit has been made available to the public and could be used for attacks.

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Meta Information

Published
2026-08-14
Last Modified
2026-08-14
Generated
2026-08-14
AI Q&A
2026-08-14
EPSS Evaluated
N/A
NVD
CVE-2026-19812
EUVD
EUVD-2026-58606

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.

Attack-Flow Graph

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Executive Summary

CVE-2026-19812 is a stack-based buffer overflow vulnerability in TOTOLINK A800R router firmware version V4.1.2cu.5137_B20200730. It occurs in the UploadCustomModule function of the /cgi-bin/cstecgi.cgi endpoint. The File parameter in user requests is processed without proper bounds checking, allowing an attacker to overflow the stack by sending a specially crafted HTTP POST request with an excessively long File parameter.

Detection Guidance

To detect this vulnerability, monitor network traffic for HTTP POST requests to /cgi-bin/cstecgi.cgi with unusually long File parameters. Use tools like Wireshark or tcpdump to capture and analyze traffic. Check router logs for crashes or unusual activity in the UploadCustomModule function.

Impact Analysis

This vulnerability can be exploited remotely without authentication. An attacker could send a malicious request to trigger memory corruption, potentially leading to arbitrary code execution on the router. This may allow unauthorized access, data theft, or disruption of network services. Publicly available exploit code increases the risk of real-world attacks.

Compliance Impact

This vulnerability could potentially impact compliance with GDPR and HIPAA by enabling remote code execution on affected devices. A successful exploit may lead to unauthorized access, data breaches, or loss of sensitive information, which are key concerns under these regulations.

Mitigation Strategies

Immediately update the TOTOLINK A800R firmware to the latest version. Disable remote access to the router's web interface if not required. Block external requests to /cgi-bin/cstecgi.cgi at the network firewall level. Monitor for suspicious activity and apply patches as soon as they become available.

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