Exim CVE-2019-15846 Arbitrary Code Execution Vulnerability

Risk

High

Date Discovered

September 2, 2019

Description

Exim is prone to an arbitrary code-execution vulnerability. An attacker can exploit this issue to execute arbitrary code with root privileges. Exim versions 4.8 through 4.92.1 are vulnerable.

Technologies Affected

  • Exim Exim 4.80
  • Exim Exim 4.80.1
  • Exim Exim 4.82
  • Exim Exim 4.82.1
  • Exim Exim 4.83
  • Exim Exim 4.84.2
  • Exim Exim 4.85
  • Exim Exim 4.85.2
  • Exim Exim 4.86
  • Exim Exim 4.86.2
  • Exim Exim 4.87
  • Exim Exim 4.88
  • Exim Exim 4.89
  • Exim Exim 4.90
  • Exim Exim 4.90.1
  • Exim Exim 4.91
  • Exim Exim 4.92
  • Exim Exim 4.92.1
  • Redhat Enterprise Linux 5
  • Ubuntu Ubuntu Linux 16.04 LTS
  • Ubuntu Ubuntu Linux 18.04 LTS
  • Ubuntu Ubuntu Linux 19.04

Recommendations

Permit local access for trusted individuals only. Where possible, use restricted environments and restricted shells.
Permit access to systems for trusted and accountable individuals only.

Block external access at the network boundary, unless external parties require service.
If global access isn't needed, filter access to the affected device at the network boundary. Restricting access to only trusted computers and networks might greatly reduce the likelihood of exploitation.

Deploy network intrusion detection systems to monitor network traffic for malicious activity.
Deploy NIDS to monitor network traffic for signs of anomalous or suspicious activity. This includes but is not limited to requests that include explained incoming and outgoing traffic. This may indicate exploit attempts to activity that results from successful exploits.

Implement multiple redundant layers of security.
Since this issue may be leveraged to execute code, we recommend memory-protection schemes, such as nonexecutable stack/heap configurations and randomly mapped memory segments. This tactic may complicate exploits of memory-corruption vulnerabilities.

Updates are available. Please see the references or vendor advisory for more information.

References

Credits

Zerons for the initial report, Qualys for the analysis


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