Which versions of TOTOLINK A800R are affected by EUVD-2026-58608?

TOTOLINK A800R router firmware 4.1.2cu.5137_B20200730 contains a vulnerability allowing authenticated remote attackers to execute arbitrary code on affected devices.

How to fix or mitigate EUVD-2026-58608?

Within 24 hours: Identify and document all TOTOLINK A800R devices running firmware 4.1.2cu.5137_B20200730; restrict administrative access through firewall rules limiting management interface connectivity to authorized personnel only, and disable remote management protocols (SSH, HTTPS admin) unless operationally required. Within 7 days: Implement network segmentation to isolate affected devices from systems containing sensitive data; deploy intrusion detection signatures to monitor for oversized Comment parameters sent to the setMacFilterRules CGI function; and enable detailed audit logging of all administrative activity. Within 30 days: Contact TOTOLINK support to determine whether patched firmware versions are available; evaluate replacement with alternative router models from vendors demonstrating active security patch velocity; and complete migration of critical network services to remediated or replacement infrastructure.

TOTOLINK A800R EUVD-2026-58608

Q: What is the CVSS score of EUVD-2026-58608?

EUVD-2026-58608 has a CVSS 4.0 base score of 7.4 (High). CVSS vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. EPSS exploitation probability: 0.6%.

| CVE-2026-19813 HIGH

Buffer Overflow (CWE-119)

2026-08-14 cna@vuldb.com

GHSA-4f74-rpch-f3gc

Buffer Overflow

7.4

CVSS 4.0 · Vendor: vuldb

Severity by source

Vendor (vuldb) PRIMARY

7.4 HIGH

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

vuln.today AI

8.8 HIGH

Network-accessible CGI endpoint requires PR:L credentials; stack overflow yields full device compromise with no scope change beyond the router itself.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (vuldb).

CVSS VectorVendor: vuldb

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Lifecycle Timeline

Analysis Generated

Aug 14, 2026 - 08:31 vuln.today

CVE Published

Aug 14, 2026 - 08:17 cve.org

HIGH 7.4

DescriptionCVE.org

A security vulnerability has been detected in TOTOLINK A800R 4.1.2cu.5137_B20200730. This impacts the function setMacFilterRules of the file /cgi-bin/cstecgi.cgi of the component firewall.so. Such manipulation of the argument Comment leads to stack-based buffer overflow. The attack may be performed from remote. The exploit has been disclosed publicly and may be used.

AnalysisAI

Stack-based buffer overflow in TOTOLINK A800R firmware 4.1.2cu.5137_B20200730 exposes authenticated remote attackers to potential arbitrary code execution by sending an oversized Comment argument to the setMacFilterRules CGI function. A public proof-of-concept has been disclosed on GitHub (corroborated by the CVSS 4.0 E:P modifier), elevating real-world risk beyond the base score of 7.4. No vendor advisory or patched firmware version has been identified at time of analysis, leaving affected devices without an official remediation path.

Technical ContextAI

The vulnerability is located in the firewall.so shared library, specifically within the setMacFilterRules function exposed through the router's web management CGI endpoint /cgi-bin/cstecgi.cgi on TOTOLINK A800R routers. CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) identifies the root cause class: the function performs an unchecked copy of the user-supplied Comment parameter into a fixed-size stack buffer, with no length validation, resulting in a classic stack-based overflow. The CGI interface serves as the router's administrative web frontend handling firewall MAC filter rule configuration. No CPE strings were provided in the intelligence data, but the affected product is explicitly identified by firmware build string 4.1.2cu.5137_B20200730, dated July 30, 2020, indicating this is a legacy firmware release.

RemediationAI

No vendor-released patch or formal TOTOLINK security advisory has been identified at time of analysis. Organizations running TOTOLINK A800R should monitor https://www.totolink.net/ for firmware updates superseding build 4.1.2cu.5137_B20200730 and apply any available update immediately. As a primary compensating control, disable remote (WAN-side) access to the router's web management interface to eliminate the network-accessible attack path - this is the most impactful single mitigation, though it may disrupt remote administration workflows. On the LAN side, restrict access to the /cgi-bin/cstecgi.cgi management endpoint to trusted management hosts using ACLs or VLAN segmentation. Additionally, ensure no default credentials remain on the device, as credential compromise is a prerequisite for exploitation given the PR:L requirement. If the MAC filter rule configuration feature is not operationally required, disabling it reduces the exposed attack surface within the CGI interface. Consider replacing end-of-life firmware devices with supported alternatives if no vendor patch materializes.