# CVE-2026-77218: PLANET GS-4210-16P2S V3 Stack Buffer Overflow via dispatcher.cgi Credential Handlers

> Authenticated attackers can trigger stack buffer overflows in the web management interface of PLANET switches, causing a denial of service.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 28 Aug 2026
- **Updated:** 1 Sep 2026
- **Also known as:** GHSA-qx7g-cv57-953h

## What is CVE-2026-77218?

CVE-2026-77218 is a medium-severity memory corruption vulnerability in PLANET GS-4210-16P2S V3, published on 28 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

PLANET GS-4210-16P2S V3 firmware before 3.441b260626 contains authenticated stack buffer overflow vulnerabilities in /cgi-bin/dispatcher.cgi. The web_login_first_post handler copies the usrPass POST parameter into a fixed-size stack buffer without length validation, the web_sys_enablePasswd_post handler copies the enbPass POST parameter into a fixed-size stack buffer without length validation, and the web_sys_localUser_post 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.

Weakness: CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2026-77218?


## How do I fix CVE-2026-77218?

No fix has been published for CVE-2026-77218 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-77218 being exploited?

There is no known exploitation of CVE-2026-77218 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77218 and fix it if it is affected.

What it is: CVE-2026-77218 is a medium-severity memory corruption vulnerability in PLANET GS-4210-16P2S V3, published on 28 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-77218 in the wild and no public exploit code.

Affected product: PLANET GS-4210-16P2S V3. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-77218/ (Markdown: https://insights.sbomify.com/CVE-2026-77218/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77218
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77218
- OSV: https://osv.dev/vulnerability/CVE-2026-77218

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77218/
Summaries are generated and may contain mistakes; the official description above is the record.