CVE-2021-43557: Apache APISIX: Path traversal in request_uri variable

[Zexuan Luo <sp...@apache.org>]

Severity: moderate

Description:

The uri-block plugin in APISIX 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.

This issue is fixed in APISIX 2.10.2.
Thanks to Marcin Niemiec for reporting the vulnerability.

Mitigation:

1. Upgrade to APISIX 2.10.2
2. Carefully review custom code, find & fix the usage of $request_uri
without verification.

Re: CVE-2021-43557: Apache APISIX: Path traversal in request_uri variable

[Zhiyuan Ju <ju...@apache.org>]

Hi,

Thanks to Marcin, and Apache APISIX's Website just published his blog about
this CVE[1].

 Welcome to read this post :)

[1] https://apisix.apache.org/blog/2021/11/23/cve-2021-43557-research-report

Best Regards!
@ Zhiyuan Ju <https://github.com/juzhiyuan>


Zexuan Luo <sp...@apache.org> 于2021年11月22日周一 下午2:30写道：

> Severity: moderate
>
> Description:
>
> The uri-block plugin in APISIX 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.
>
> This issue is fixed in APISIX 2.10.2.
> Thanks to Marcin Niemiec for reporting the vulnerability.
>
> Mitigation:
>
> 1. Upgrade to APISIX 2.10.2
> 2. Carefully review custom code, find & fix the usage of $request_uri
> without verification.
>