# CVE-2026-121600: TOTOLINK A950RG stack buffer overflow in MAC filter handler

Source: https://junglewise.ai/threats/cve-2026-121600-a-flaw-has-been-found-in-totolink-a950rg-4-1-2cu-5268-b20221104  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-04. Updated: 2026-11-04  
License: CC BY 4.0 with a link back

CVE-2026-121600 · Severity: critical · CVSS 9.9 · Published 2026-11-04

The TOTOLINK A950RG router's MAC filter configuration feature is vulnerable to a stack-based buffer overflow that allows a remote attacker with network access to execute arbitrary code on the device. An attacker can craft a malicious request with an excessively long MAC address or comment field to overwrite the return address on the stack, gaining complete control of the router. This could lead to data interception, unauthorized network access, or complete compromise of the router's security functions.

Technologies: [TOTOLINK A950rg](https://junglewise.ai/threats/technologies/a950rg). Vendors: [TOTOLINK](https://junglewise.ai/threats/vendors/totolink).

## Quick answers

**Is CVE-2026-121600 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-121600 being exploited in the wild.

**How severe is CVE-2026-121600?** Critical severity, with a CVSS score of 9.9, published 4 November 2026.

**Which products and versions are affected?** TOTOLINK A950rg 4.1.2cu.5268_B20221104.

**Is there a fix for CVE-2026-121600?** 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-2026-121600 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-121600?** Check whether you run TOTOLINK A950rg 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

The vulnerability exists in the setMacFilterRules function within the MAC Filter Handler component (/cgi-bin/cstecgi.cgi). A 4-byte stack buffer for MAC address filtering is overrun via an unbounded character-copying loop that accepts 17+ character MAC addresses, and a 68-byte comment buffer is overrun via unbounded strcpy and strcat operations that accept 93+ byte comments. Both overflows corrupt the saved return address (92 bytes from comment buffer start) on a non-PIE, non-stack-protected target with no ASLR, allowing arbitrary code execution at a fixed address.

## Affected products

- TOTOLINK A950RG 4.1.2cu.5268_B20221104

## Timeline

- 2026-11-04: disclosed

## References

- [https://gist.github.com/H3rmesk1t/217c00b12e04fcde07c453a55579f808](https://gist.github.com/H3rmesk1t/217c00b12e04fcde07c453a55579f808)
- [https://vuldb.com/cve/CVE-2026-121600](https://vuldb.com/cve/CVE-2026-121600)

## Related threats

- [TOTOLINK A950RG stack buffer overflow in WiFi configuration](https://junglewise.ai/threats/cve-2026-121599-a-vulnerability-was-detected-in-totolink-a950rg-4-1-2cu-5268)
- [TOTOLINK A950RG stack buffer overflow in wireless configuration](https://junglewise.ai/threats/cve-2026-121598-a-security-vulnerability-has-been-detected-in-totolink-a950rg-4)
- [TOTOLINK A950RG stack buffer overflow in Easy Setup Wizard](https://junglewise.ai/threats/cve-2026-121597-a-weakness-has-been-identified-in-totolink-a950rg-4-1-2cu-5268)
- [TOTOLINK A950RG stack buffer overflow in infostat.cgi](https://junglewise.ai/threats/cve-2026-116508-a-security-flaw-has-been-discovered-in-totolink-a950rg-4-1-2cu)
- [TOTOLINK A950RG information disclosure in getLanguageCfg](https://junglewise.ai/threats/cve-2026-116507-a-vulnerability-was-identified-in-totolink-a950rg-4-1-2cu-5268)