# CVE-2026-5688: Totolink A7100RU OS command injection in setDdnsCfg

Source: https://junglewise.ai/threats/cve-2026-5688-totolink-a7100ru-os-command-injection-in-setddnscfg  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-06. Updated: 2026-07-24  
License: CC BY 4.0 with a link back

CVE-2026-5688 · Severity: high · CVSS 7.3 · Published 2026-04-06

A security vulnerability exists in the Totolink A7100RU wireless router, a device used to provide home and business internet connectivity. An attacker can remotely send a specially crafted request to the router's management interface to take control of the device. This could allow an unauthorized user to disrupt internet service, monitor network traffic, or use the router as a foothold to attack other devices on the local network.

Technologies: [TOTOLINK A7100ru](https://junglewise.ai/threats/technologies/a7100ru). Vendors: [TOTOLINK](https://junglewise.ai/threats/vendors/totolink).

## Quick answers

**Is CVE-2026-5688 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-5688 being exploited in the wild.

**How severe is CVE-2026-5688?** High severity, with a CVSS score of 7.3, published 6 April 2026.

**Which products and versions are affected?** TOTOLINK A7100ru 7.4cu.2313_b20191024.

**Is there a fix for CVE-2026-5688?** 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-2026-5688 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-5688?** Check whether you run TOTOLINK A7100ru 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 A7100RU router firmware version 7.4cu.2313_b20191024. The flaw is located within the 'setDdnsCfg' function of the '/cgi-bin/cstecgi.cgi' binary. The application fails to properly sanitize the 'provider' parameter before passing it to the 'CsteSystem' function, which eventually executes the input via 'execv()'. A remote, unauthenticated attacker can exploit this by sending a crafted POST request containing shell metacharacters (e.g., backticks) in the JSON payload. Successful exploitation allows for arbitrary command execution with the privileges of the web server. A public PoC demonstrating the use of 'wget' for command execution has been disclosed.

## Affected products

- Totolink A7100RU 7.4cu.2313_b20191024

## Timeline

- 2026-04-06: disclosed: Initial public disclosure via VulDB and GitHub PoC
- 2026-04-06: advisory: CVE-2026-5688 published

## References

- [https://github.com/Litengzheng/vuldb_new/blob/main/A7100RU/vul_186/README.md](https://github.com/Litengzheng/vuldb_new/blob/main/A7100RU/vul_186/README.md)
- [https://vuldb.com/submit/792945](https://vuldb.com/submit/792945)
- [https://vuldb.com/vuln/355515](https://vuldb.com/vuln/355515)
- [https://vuldb.com/vuln/355515/cti](https://vuldb.com/vuln/355515/cti)
- [https://www.totolink.net/](https://www.totolink.net/)

## Related threats

- [Totolink A7100RU command injection in setGameSpeedCfg](https://junglewise.ai/threats/cve-2026-5692-totolink-a7100ru-command-injection-in-setgamespeedcfg)
- [Totolink A7100RU command injection in setFirewallType](https://junglewise.ai/threats/cve-2026-5691-totolink-a7100ru-command-injection-in-setfirewalltype)
- [Totolink A7100RU OS command injection in setRemoteCfg](https://junglewise.ai/threats/cve-2026-5690-totolink-a7100ru-os-command-injection-in-setremotecfg)
- [Totolink A7100RU command injection in setNtpCfg](https://junglewise.ai/threats/cve-2026-5689-totolink-a7100ru-command-injection-in-setntpcfg)
- [Totolink A7100RU OS command injection in cstecgi.cgi](https://junglewise.ai/threats/cve-2026-5678-totolink-a7100ru-os-command-injection-in-cstecgi-cgi)