# CVE-2026-75126: PLANET GS-4210-16P2S V3 stack buffer overflow in dispatcher.cgi handlers

Source: https://junglewise.ai/threats/cve-2026-75126-planet-gs-4210-16p2s-v3-stack-buffer-overflow-in-dispatcher-cgi  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-28. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-75126 · Severity: medium · CVSS 4.9 · Published 2026-08-28

The PLANET GS-4210-16P2S V3 is a managed network switch with web-based administration. Multiple web management handlers fail to validate the length of user-supplied configuration parameters, allowing an authenticated administrator to trigger stack buffer overflows. An attacker with valid admin credentials can crash the web management service, causing temporary unavailability of remote device administration and configuration.

Technologies: [PLANET GS-4210-16P2S V3](https://junglewise.ai/threats/technologies/gs-4210-16p2s-v3). Vendors: [PLANET](https://junglewise.ai/threats/vendors/planet).

## Quick answers

**Is CVE-2026-75126 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-75126 being exploited in the wild.

**How severe is CVE-2026-75126?** Medium severity, with a CVSS score of 4.9, published 28 August 2026.

**Which products and versions are affected?** PLANET GS-4210-16P2S V3 before 3.441b260626.

**Is there a fix for CVE-2026-75126?** A patch was published on 2026-08-28: Patched firmware version 3.441b260626 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-75126 attacked?** It is attacked over the network, in device firmware.

**Am I affected by CVE-2026-75126?** Check whether you run PLANET GS-4210-16P2S V3 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 is a stack-based buffer overflow (CWE-121) affecting 30+ authenticated POST handlers in /cgi-bin/dispatcher.cgi. The affected handlers (web_vlan_membership_edit_dialog_post, web_snmp_v3view_add_post, web_dhcp_option82_post, and others) copy attacker-controlled POST parameters directly into fixed-size stack buffers without length validation. An authenticated attacker with administrator-level web-management privileges can send oversized POST parameters to overflow the stack, crash the CGI process, and disrupt the web management interface. The attack requires valid authentication credentials and network access to the web management port. Patched firmware version 3.441b260626 and later addresses this issue by implementing proper buffer length validation.

## Affected products

- PLANET GS-4210-16P2S V3 before 3.441b260626

## Timeline

- 2026-08-28: disclosed
- 2026-08-28: patched: Patched firmware version 3.441b260626 released

## References

- [https://www.planet.com.tw/en/support/security-advisory/10](https://www.planet.com.tw/en/support/security-advisory/10)
- [https://www.vulncheck.com/advisories/planet-gs-4210-16p2s-stack-buffer-overflow-via-dispatcher-cgi-standard-handlers](https://www.vulncheck.com/advisories/planet-gs-4210-16p2s-stack-buffer-overflow-via-dispatcher-cgi-standard-handlers)

## Related threats

- [PLANET GS-4210-16P2S V3 stack buffer overflow in dispatcher.cgi](https://junglewise.ai/threats/cve-2026-77218-planet-gs-4210-16p2s-v3-stack-buffer-overflow-in-dispatcher-cgi)
- [PLANET GS-4210-16P2S V3 stack buffer overflow in RADIUS handlers](https://junglewise.ai/threats/cve-2026-77217-planet-gs-4210-16p2s-v3-stack-buffer-overflow-in-radius-handlers)
- [PLANET GS-4210-16P2S V3 null pointer dereference in dispatcher.cgi](https://junglewise.ai/threats/cve-2026-75125-planet-gs-4210-16p2s-v3-null-pointer-dereference-in-dispatcher)
- [PLANET GS-4210-16P2S V3 pre-authentication memory corruption](https://junglewise.ai/threats/cve-2026-75124-planet-gs-4210-16p2s-v3-pre-authentication-memory-corruption)
- [PLANET GS-4210-16P2S V3 OS command injection in dispatcher.cgi](https://junglewise.ai/threats/cve-2026-75123-planet-gs-4210-16p2s-v3-os-command-injection-in-dispatcher-cgi)