CVE-2026-77218: PLANET GS-4210-16P2S V3 Stack Buffer Overflow via dispatcher.cgi Credential Handlers
PLANET GS-4210-16P2S V3 firmware before 3.441b260626 contains authenticated stack buffer overflow vulnerabilities in /cgi-bin/dispatcher.cgi. The webloginfirstpost handler copies the usrPass POST parameter into a fixed-size stack buffer without length validation, the websysenablePasswdpost handler copies the enbPass POST parameter into a fixed-size stack buffer without length validation, and the websyslocalUserpost handler copies the usrName and usrPass POST parameters into fixed-size stack buffers without length validation. A remote authenticated attacker can send a crafted request to crash the CGI process or web management service, resulting in denial of service.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
PLANET GS-4210-16P2S V3 firmwareto a version that resolves this vulnerability.Fixed in 3.441b260626 - Compensating control
Mitigate denial of service by limiting access to the web management interface/CGI endpoints (including /cgi-bin/dispatcher.cgi handlers web_login_first_post, web_sys_enablePasswd_post, and web_sys_localUser_post) to trusted sources only until the firmware is upgraded.
Event History
Frequently Asked Questions
Who can exploit this issue?
An attacker must be remotely able to reach the device's web management interface and authenticate. The available impact is denial of service through a crash of the CGI process or web management service.
Which credential-management actions are affected?
The affected dispatcher.cgi handlers process login passwords, enable passwords, and local user names and passwords. The relevant POST parameters are usrPass, enbPass, and usrName.
How can I determine whether a device is affected?
Devices running firmware earlier than 3.441b260626 are affected. Verify the installed firmware version on the GS-4210-16P2S and update if it is below that version.