Use-after-free error in Exim - CVE-2017-16943
Published: November 28, 2017 / Updated: February 5, 2018
Vulnerability identifier: #VU9427
CSH Severity: High
CVSS v4.0: 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
Vendor: Exim
Affected software:
Exim
Exim
Detailed vulnerability 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.
How to mitigate CVE-2017-16943
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."