# CVE-2026-9387: Totolink A8000RU command injection in setUpgradeFW

Source: https://junglewise.ai/threats/cve-2026-9387-totolink-a8000ru-command-injection-in-setupgradefw  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-24. Updated: 2026-05-26  
License: CC BY 4.0 with a link back

CVE-2026-9387 · Severity: critical · CVSS 9.8 · Published 2026-05-24

A critical security vulnerability exists in the Totolink A8000RU wireless router, a device used to provide internet connectivity in homes and small offices. An attacker can remotely take full control of the router by sending a specially crafted request to its web management interface. This could allow an unauthorized user to intercept network traffic, disrupt internet service, or use the device as a foothold to attack other devices on the local network.

Technologies: [TOTOLINK A8000RU](https://junglewise.ai/threats/technologies/a8000ru). Vendors: [TOTOLINK](https://junglewise.ai/threats/vendors/totolink).

## Quick answers

**Is CVE-2026-9387 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-9387 being exploited in the wild.

**How severe is CVE-2026-9387?** Critical severity, with a CVSS score of 9.8, published 24 May 2026.

**Which products and versions are affected?** TOTOLINK A8000RU 7.1cu.643_b20200521.

**Is there a fix for CVE-2026-9387?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-9387 attacked?** It is attacked over the network, in device firmware.

**Am I affected by CVE-2026-9387?** Check whether you run TOTOLINK A8000RU at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An OS command injection vulnerability exists in the Totolink A8000RU firmware version 7.1cu.643_b20200521. The flaw is located within the 'setUpgradeFW' function of the '/cgi-bin/cstecgi.cgi' component. The application fails to properly sanitize the 'resetFlags' argument before passing it to 'snprintf' and subsequently executing it via 'execv()' through the 'CsteSystem' function. A remote, unauthenticated attacker can exploit this by sending a crafted POST request containing shell metacharacters (e.g., backticks) in the 'resetFlags' parameter. Successful exploitation allows for arbitrary command execution on the underlying Linux operating system. A public exploit (PoC) has been released.

## Affected products

- Totolink A8000RU 7.1cu.643_b20200521

## Timeline

- 2026-05-24: disclosed: Vulnerability details and PoC published by researcher.
- 2026-05-24: advisory: CVE-2026-9387 published.

## References

- [https://github.com/Litengzheng/vuldb_new2/blob/main/A8000RU/vul_334/README.md](https://github.com/Litengzheng/vuldb_new2/blob/main/A8000RU/vul_334/README.md)
- [https://vuldb.com/submit/813433](https://vuldb.com/submit/813433)
- [https://vuldb.com/vuln/365350](https://vuldb.com/vuln/365350)
- [https://vuldb.com/vuln/365350/cti](https://vuldb.com/vuln/365350/cti)
- [https://www.totolink.net/](https://www.totolink.net/)

## Related threats

- [Totolink A8000RU OS command injection in setParentalRules](https://junglewise.ai/threats/cve-2026-9478-totolink-a8000ru-os-command-injection-in-setparentalrules)
- [Totolink A8000RU command injection in setAccessDeviceCfg](https://junglewise.ai/threats/cve-2026-9477-totolink-a8000ru-command-injection-in-setaccessdevicecfg)
- [Totolink A8000RU command injection in setPasswordCfg](https://junglewise.ai/threats/cve-2026-9476-totolink-a8000ru-command-injection-in-setpasswordcfg)
- [Totolink A8000RU command injection in setIpQosRules](https://junglewise.ai/threats/cve-2026-9475-totolink-a8000ru-command-injection-in-setipqosrules)
- [Totolink A8000RU OS command injection in setWanCfg](https://junglewise.ai/threats/cve-2026-9458-totolink-a8000ru-os-command-injection-in-setwancfg)