#VU9427 Use-after-free error in Exim - CVE-2017-16943
Published: November 28, 2017 / Updated: February 5, 2018
Vulnerability identifier: #VU9427
Vulnerability risk: High
CVSSv4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: CVE-2017-16943
CWE-ID: CWE-416
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerable software:
Exim
Exim
Software vendor:
Exim
Exim
Description
The vulnerability allows a remote attacker to execute arbitrary code on the target system.
The weakness exists due to a use-after-free memory error in the ESMTP CHUNKING extension within the receive_msg() function in receive.c. A remote attacker can connect to the SMTP service, send a specially crafted BDAT command, trigger memory corruption and execute arbitrary code on the target system.
Successful exploitation of the vulnerability may result in system compromise.
The weakness exists due to a use-after-free memory error in the ESMTP CHUNKING extension within the receive_msg() function in receive.c. A remote attacker can connect to the SMTP service, send a specially crafted BDAT command, trigger memory corruption and execute arbitrary code on the target system.
Successful exploitation of the vulnerability may result in system compromise.
Remediation
Update to version 4.90.
The vendor has described a workaround:
".. in the main section of your Exim configuration, set:
chunking_advertise_hosts =
This disables advertising the ESMTP CHUNKING extension, making the BDAT verb unavailable and avoids letting an attacker apply the logic."
The vendor has described a workaround:
".. in the main section of your Exim configuration, set:
chunking_advertise_hosts =
This disables advertising the ESMTP CHUNKING extension, making the BDAT verb unavailable and avoids letting an attacker apply the logic."