[ASA-201903-7] pacman: arbitrary code execution

[Levente Polyak]

Arch Linux Security Advisory ASA-201903-7
=========================================

Severity: High
Date    : 2019-03-11
CVE-ID  : CVE-2019-9686
Package : pacman
Type    : arbitrary code execution
Remote  : Yes
Link    : https://security.archlinux.org/AVG-921

Summary
=======

The package pacman before version 5.1.3-1 is vulnerable to arbitrary
code execution.

Resolution
==========

Upgrade to 5.1.3-1.

# pacman -Syu "pacman>=5.1.3-1"

The problem has been fixed upstream in version 5.1.3.

Workaround
==========

None.

Description
===========

pacman prior to version 5.1.3 allows directory traversal when
installing a remote package via a specified URL "pacman -U <url>" due
to an unsanitized file name received from a Content-Disposition header.
pacman renames the downloaded package file to match the name given in
this header. However, pacman did not sanitize this name, which may
contain slashes, before calling rename(). A malicious server (or a
network MitM if downloading over HTTP) can send a Content-Disposition
header to make pacman place the file anywhere in the filesystem,
potentially leading to arbitrary root code execution. Notably, this
bypasses pacman's package signature checking. This occurs in
curl_download_internal in lib/libalpm/dload.c.

Impact
======

A remote attacker in the position of man-in-the-middle or a malicious
server is able to execute arbitrary code as root when a user installs a
remote package via a specified URL.

References
==========

https://git.archlinux.org/pacman.git/commit/?id=9702703633bec2c007730006de2aeec8587dfc84
https://git.archlinux.org/pacman.git/commit/?id=d197d8ab82cf10650487518fb968067897a12775
https://git.archlinux.org/pacman.git/commit/?h=release/5.1.x&id=1bf767234363f7ad5933af3f7ce267c123017bde
https://security.archlinux.org/CVE-2019-9686

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