[arch-security] [ASA-201706-22] lib32-glibc: privilege escalation

[Levente Polyak]

Arch Linux Security Advisory ASA-201706-22
==========================================

Severity: High
Date    : 2017-06-20
CVE-ID  : CVE-2017-1000366
Package : lib32-glibc
Type    : privilege escalation
Remote  : No
Link    : https://security.archlinux.org/AVG-308

Summary
=======

The package lib32-glibc before version 2.25-4 is vulnerable to
privilege escalation.

Resolution
==========

Upgrade to 2.25-4.

# pacman -Syu "lib32-glibc>=2.25-4"

The problem has been fixed upstream but no release is available yet.

Workaround
==========

None.

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

A flaw was found in the way memory was being allocated on the stack for
user space binaries. If heap (or different memory region) and stack
memory regions were adjacent to each other, an attacker could use this
flaw to jump over the stack guard gap, cause controlled memory
corruption on process stack or the adjacent memory region, and thus
increase their privileges on the system. This is glibc-side mitigation
which blocks processing of LD_LIBRARY_PATH for programs running in
secure-execution mode and reduces the number of allocations performed
by the processing of LD_AUDIT, LD_PRELOAD, and LD_HWCAP_MASK, making
successful exploitation of this issue more difficult.

Impact
======

A local attacker is able to execute arbitrary code on the affected host
that is effectively leading to elevation of privileges by choosing a
suitable target application.

References
==========

https://www.qualys.com/2017/06/19/stack-clash/stack-clash.txt
https://security.archlinux.org/CVE-2017-1000366

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