DD-WRT Stack-Based Buffer Overflow Vulnerability

DD-WRT DD-WRT

DD-WRT contains a stack-based buffer overflow vulnerability that could allow an unauthenticated attacker to overflow an internal buffer used by UPnP and trigger a code execution vulnerability. Added to CISA KEV on 2026-07-21 (federal deadline 2026-07-24).

First seen: 21 Jul 2026
Last update: 21 Jul 2026, 12:00 UTC
Identifiers: CVE-2021-27137
Source: CISA KEV

Check this repository for exposure to one security incident from pwned.coffee. Report first, change nothing until I say so.

## DD-WRT Stack-Based Buffer Overflow Vulnerability
Severity: high, exploited in the wild. Patch status: patched.
Affected: DD-WRT DD-WRT
Ids: CVE-2021-27137

DD-WRT contains a stack-based buffer overflow vulnerability that could allow an unauthenticated attacker to overflow an internal buffer used by UPnP and trigger a code execution vulnerability. Added to CISA KEV on 2026-07-21 (federal deadline 2026-07-24).

## Steps
1. Search the repo, its CI and infra config for DD-WRT DD-WRT. If present, report the version in use and whether it's affected.

## Report
A table: file, product or package, version in use, affected yes/no, exact fix. Then anything a human has to check outside the repo.

If you have the pwned.coffee MCP server (https://pwned.coffee/mcp), call lookup_cve("CVE-2021-27137") for the latest, and check_repo with this repo's lockfiles, Dockerfiles and workflows for a full receipt.
Sources: https://nvd.nist.gov/vuln/detail/CVE-2021-27137
https://pwned.coffee/i/dd-wrt-stack-based-buffer-overflow-vulnerability-cve-2021-27137

Sources

NVD: CVE-2021-27137

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