Arch Linux: 201711-32 Critical: Exim Arbitrary Code Execution

The package exim before version 4.89.1-1 is vulnerable to multiple issues including arbitrary code execution, denial of service and information disclosure.

Arch Linux Security Advisory ASA-201711-32
=========================================
Severity: Critical
Date    : 2017-11-30
CVE-ID  : CVE-2017-1000369 CVE-2017-10140 CVE-2017-16943 CVE-2017-16944
Package : exim
Type    : multiple issues
Remote  : Yes
Link    : https://security.archlinux.org/AVG-518

Summary
======
The package exim before version 4.89.1-1 is vulnerable to multiple
issues including arbitrary code execution, denial of service and
information disclosure.

Resolution
=========
Upgrade to 4.89.1-1.

# pacman -Syu "exim>=4.89.1-1"

The problems have been fixed upstream in version 4.89.1.

Workaround
=========
None.

Description
==========
- CVE-2017-1000369 (denial of service)

An uncontrolled resource consumption flaw has been discovered in Exim
before 4.89.1. The use of multiple "-p" command line arguments which
are malloc()'ed and never free()'ed results in leaking memory. While
Exim itself is not vulnerable to privilege escalation, this particular
flaw can be used by the stackguard vulnerability to achieve privilege
escalation.

- CVE-2017-10140 (information disclosure)

It was found that Berkeley DB reads the DB_CONFIG configuration file
from the current working directory by default. This happens when
calling db_create() with dbenv=NULL; or using the dbm_open() function.
This behavior leads to a security vulnerability because in the case of
setuid or setgid commands, excerpts of the file are revealed to the
calling user (and maybe more harm could be done with specially crafted
DB_CONFIG files).

- CVE-2017-16943 (arbitrary code execution)

The receive_msg function in receive.c in the SMTP daemon in Exim 4.88
and 4.89 allows remote attackers to execute arbitrary code or cause a
denial of service (use-after-free) via vectors involving BDAT commands.

- CVE-2017-16944 (denial of service)

The receive_msg function in receive.c in the SMTP daemon in Exim 4.88
and 4.89 allows remote attackers to cause a denial of service (infinite
loop and stack exhaustion) via vectors involving BDAT commands and an
improper check for a '.' character signifying the end of the content,
related to the bdat_getc function.

Impact
=====
A remote attacker is able to crash the application or execute arbitrary
code on the affected host. A local attacker is able to bypass access
restrictions to obtain sensitive data from local files or bypass the
stack guard to elevate privileges on the system.

References
=========
https://bugs.archlinux.org/task/56478
https://www.qualys.com/2017/06/19/stack-clash/stack-clash.txt
https://code.exim.org/exim/exim
https://access.redhat.com/security/vulnerabilities/stackguard
https://seclists.org/oss-sec/2017/q2/452
http://www.postfix.org/announcements/postfix-3.2.2.html
https://code.exim.org/exim/exim
https://www.openwall.com/lists/oss-security/2017/11/25/2
https://bugs.exim.org/show_bug.cgi?id=2199
https://code.exim.org/exim/exim
https://github.com/LetUsFsck/PoC-Exploit-Mirror/tree/master/CVE-2017-16944
https://lists.exim.org/lurker/message/20171125.034842.d1d75cac.en.html
https://bugs.exim.org/show_bug.cgi?id=2201
https://code.exim.org/exim/exim
https://www.exploit-db.com/exploits/43184
https://security.archlinux.org/CVE-2017-1000369
https://security.archlinux.org/CVE-2017-10140
https://security.archlinux.org/CVE-2017-16943
https://security.archlinux.org/CVE-2017-16944