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Date: Sat, 16 Aug 2014 02:12:41 -0400 (EDT)
From: cve-assign@...re.org
To: carnil@...ian.org
Cc: cve-assign@...re.org, oss-security@...ts.openwall.com
Subject: Re: CVE Request: Plack::App::File does not prune trailing slashes: possible code exposure / information disclosure

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>    - Plack::App::File would previously strip trailing slashes off
>      provided paths. This in combination with the common pattern
>      of serving files with Plack::Middleware::Static could allow
>      an attacker to bypass a whitelist of generated files
> 
> http://api.metacpan.org/source/MIYAGAWA/Plack-1.0031/Changes
> https://github.com/plack/Plack/issues/405

The underlying issue is that Plack::App::File allowed a trailing slash
in a pathname referring to a plain file. There is at least one
specification suggesting that this is wrong:

  http://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_xbd_chap04.html#tag_21_04_12

  Pathnames that end with one or more trailing <slash> characters must
  refer to directory paths. Earlier versions of this standard were not
  specific about the distinction between trailing <slash> characters
  on files and directories, and both were permitted.

Without going into the question of whether Plack is responsible for
following that specification, it seems that the vendor identified
arguably wrong behavior that had a security impact, and fixed it. Use
CVE-2014-5269.

(In some related but non-identical situations -- for example, if a
product decided to reject a valid pathname such as /etc//// as a
possibly misguided attempt at security hardening -- there wouldn't be
a CVE ID.)

- -- 
CVE assignment team, MITRE CVE Numbering Authority
M/S M300
202 Burlington Road, Bedford, MA 01730 USA
[ PGP key available through http://cve.mitre.org/cve/request_id.html ]
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