CVE-2017-10621

Junos OS: Denial of service vulnerability in telnetd

Description

A denial of service vulnerability in telnetd service on Juniper Networks Junos OS allows remote unauthenticated attackers to cause a denial of service. Affected Junos OS releases are: 12.1X46 prior to 12.1X46-D71; 12.3X48 prior to 12.3X48-D50; 14.1 prior to 14.1R8-S5, 14.1R9; 14.1X53 prior to 14.1X53-D50; 14.2 prior to 14.2R7-S9, 14.2R8; 15.1 prior to 15.1F2-S16, 15.1F5-S7, 15.1F6-S6, 15.1R5-S2, 15.1R6; 15.1X49 prior to 15.1X49-D90; 15.1X53 prior to 15.1X53-D47; 16.1 prior to 16.1R4-S1, 16.1R5; 16.2 prior to 16.2R1-S3, 16.2R2;

Remediation

Workaround:

  • Disabling the telnet service would completely mitigate this issue. Reducing the maximum number of connections to a value between 1 and 250 would help mitigate this vulnerability. For example: user@junos# set system services telnet connection-limit 100
  • It is good security practice to limit the exploitable attack surface of critical infrastructure networking equipment. Use access lists or firewall filters to limit access to the device from trusted, administrative networks or hosts.

Category

5.3
CVSS
Severity: Medium
CVSS 3.0 •
CVSS 2.0 •
EPSS 0.35%
Vendor Advisory juniper.net
Affected: Juniper Networks Junos OS
Published at:
Updated at:

References

Link Tags
https://kb.juniper.net/JSA10817 mitigation vendor advisory

Frequently Asked Questions

What is the severity of CVE-2017-10621?
CVE-2017-10621 has been scored as a medium severity vulnerability.
How to fix CVE-2017-10621?
As a workaround for remediating CVE-2017-10621: Disabling the telnet service would completely mitigate this issue. Reducing the maximum number of connections to a value between 1 and 250 would help mitigate this vulnerability. For example: user@junos# set system services telnet connection-limit 100
Is CVE-2017-10621 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2017-10621 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2017-10621?
CVE-2017-10621 affects Juniper Networks Junos OS.
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