full-disclosure - Re: [FD] cpio privilege escalation vulnerability via setuid files in cpio archive

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Message-ID: <dbaf3853-3cc9-78dd-9241-5cc4c111416f@sintonen.fi>
Date: Tue, 9 Jan 2024 00:45:39 +0200 (EET)
From: Harry Sintonen via Fulldisclosure <fulldisclosure@...lists.org>
To: Georgi Guninski <gguninski@...il.com>
Cc: Harry Sintonen <harry@...tonen.fi>, fulldisclosure@...lists.org
Subject: Re: [FD] cpio privilege escalation vulnerability via setuid files
 in cpio archive

On Mon, 8 Jan 2024, Georgi Guninski wrote:

> When extracting archives cpio (at least version 2.13) preserves
> the setuid flag, which might lead to privilege escalation.

So does for example tar. The same rules that apply to tar also apply to 
cpio:

"Extract from an untrusted archive only into an otherwise-empty directory. 
This directory and its parent should be accessible only to trusted users."

> One example is r00t extracts to /tmp/ and scidiot runs /tmp/micq/backd00r
> without further interaction from root.
>
> We believe this is vulnerability, since directory traversal in cpio
> is considered vulnerability.

This is a user error, not a vulnerability in cpio.
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