Remote code execution in Exim



Published: 2017-11-28 | Updated: 2018-02-05
Risk High
Patch available YES
Number of vulnerabilities 1
CVE-ID CVE-2017-16943
CWE-ID CWE-416
Exploitation vector Network
Public exploit N/A
Vulnerable software
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Exim
Server applications / Mail servers

Vendor Exim

Security Bulletin

This security bulletin contains one high risk vulnerability.

1) Use-after-free error

EUVDB-ID: #VU9427

Risk: High

CVSSv3.1:

CVE-ID: CVE-2017-16943

CWE-ID: CWE-416 - Use After Free

Exploit availability: No

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.

Mitigation

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."

Vulnerable software versions

Exim: 4.88 - 4.89


CPE2.3 External links

http://git.exim.org/exim.git/commitdiff/4e6ae6235c68de243b1c2419027472d7659aa2b4

Q & A

Can this vulnerability be exploited remotely?

How the attacker can exploit this vulnerability?

Is there known malware, which exploits this vulnerability?



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