Bug 1517680 (CVE-2017-16943)

Summary: CVE-2017-16943 exim: use-after-free in receive_msg function via vectors involving BDAT commands
Product: [Other] Security Response Reporter: Adam Mariš <amaris>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED NOTABUG QA Contact:
Severity: urgent Docs Contact:
Priority: urgent    
Version: unspecifiedCC: bennie.joubert, dwmw2, jskarvad, tremble
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Fixed In Version: Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2017-11-27 09:02:33 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Bug Depends On: 1517686, 1517687    
Bug Blocks:    

Description Adam Mariš 2017-11-27 08:47:06 UTC
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.

Upstream bug:


Upstream patch:


Comment 1 Adam Mariš 2017-11-27 08:54:14 UTC
Created exim tracking bugs for this issue:

Affects: epel-all [bug 1517686]
Affects: fedora-all [bug 1517687]

Comment 2 Adam Mariš 2017-11-27 08:56:38 UTC

if you are running Exim 4.88 or newer, then 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.