#VU6697 Denial of service in Allen-Bradley MicroLogix 1400 and Allen-Bradley MicroLogix 1100 - CVE-2017-7901

Vulnerability identifier: #VU6697

Vulnerability risk: Low

CVSSv4.0: 1.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2017-7901

CWE-ID: CWE-343

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Allen-Bradley MicroLogix 1400
Hardware solutions / Office equipment, IP-phones, print servers
Allen-Bradley MicroLogix 1100
Hardware solutions / Office equipment, IP-phones, print servers

Vendor: Rockwell Automation

Description
The vulnerability allows a remote attacker to cause DoS condition on the target system.

The vulnerability exists due to generation of insufficiently random TCP initial sequence numbers. A remote attacker can predict the numbers from previous values and spoof or disrupt TCP connections.

Successful exploitation of the vulnerability may result in denial of service.

Mitigation
Update to version 21.00

Vulnerable software versions

Allen-Bradley MicroLogix 1400: 1766-L32AWAA 16.00 - 1766-L32AWA 16.00

Allen-Bradley MicroLogix 1100: 1763-L16DWD 16.00 - 1763-L16AWA 16.00

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External links
https://ics-cert.us-cert.gov/advisories/ICSA-17-115-04

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.