# CVE-2026-123957: TOTOLINK CA300-PoE buffer overflow in setIpQosRules

Source: https://junglewise.ai/threats/cve-2026-123957-a-vulnerability-was-determined-in-totolink-ca300-poe-6-2c-884  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-07. Updated: 2026-11-07  
License: CC BY 4.0 with a link back

CVE-2026-123957 · Severity: critical · CVSS 9.9 · Published 2026-11-07

TOTOLINK CA300-PoE is a network device that manages IP quality of service settings. A buffer overflow vulnerability in the setIpQosRules function allows an attacker to send a malicious request over the network and crash the device or execute arbitrary code with full control, potentially compromising all network traffic passing through it.

Technologies: [TOTOLINK CA300-PoE](https://junglewise.ai/threats/technologies/ca300-poe). Vendors: [TOTOLINK](https://junglewise.ai/threats/vendors/totolink).

## Quick answers

**Is CVE-2026-123957 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-123957 being exploited in the wild.

**How severe is CVE-2026-123957?** Critical severity, with a CVSS score of 9.9, published 7 November 2026.

**Which products and versions are affected?** TOTOLINK CA300-PoE 6.2c.884.

**Is there a fix for CVE-2026-123957?** 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-2026-123957 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-123957?** Check whether you run TOTOLINK CA300-PoE 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

A stack-based buffer overflow exists in the setIpQosRules function of /cgi-bin/cstecgi.cgi when processing the ipStart parameter. The vulnerability can be exploited remotely without authentication via a specially crafted HTTP request, leading to code execution on the affected device.

## Affected products

- TOTOLINK CA300-PoE 6.2c.884

## Timeline

- 2026-11-07: disclosed

## References

- [https://lavender-bicycle-a5a.notion.site/TOTOLINK-CA300-PoE-setIpQosRules-3f953a41781f801195e5e07dfe7488b9?source=copy_link](https://lavender-bicycle-a5a.notion.site/TOTOLINK-CA300-PoE-setIpQosRules-3f953a41781f801195e5e07dfe7488b9?source=copy_link)
- [https://vuldb.com/cve/CVE-2026-123957](https://vuldb.com/cve/CVE-2026-123957)

## Related threats

- [TOTOLINK CA300-PoE buffer overflow in UploadCustomModule](https://junglewise.ai/threats/cve-2026-124060-a-vulnerability-was-detected-in-totolink-ca300-poe-6-2c-884)
- [TOTOLINK CA300-PoE buffer overflow in WiFi configuration](https://junglewise.ai/threats/cve-2026-124059-a-security-vulnerability-has-been-detected-in-totolink-ca300-poe)
- [TOTOLINK CA300-PoE buffer overflow in WiFi repeater configuration](https://junglewise.ai/threats/cve-2026-124058-a-weakness-has-been-identified-in-totolink-ca300-poe-6-2c-884)
- [TOTOLINK CA300-PoE buffer overflow in setWiFiMultipleConfig](https://junglewise.ai/threats/cve-2026-124057-a-security-flaw-has-been-discovered-in-totolink-ca300-poe-6-2c)
- [TOTOLINK CA300-PoE buffer overflow in setWiFiBasicConfig](https://junglewise.ai/threats/cve-2026-123961-a-security-vulnerability-has-been-detected-in-totolink-ca300-poe)