A local privilege escalation vulnerability in Juniper Networks Junos OS and Junos OS Evolved allows a local, low-privileged user to cause the Juniper DHCP daemon (jdhcpd) process to crash, resulting in a Denial of Service (DoS), or execute arbitrary commands as root. Continued processing of malicious user-controlled input will repeatedly crash the system and sustain the Denial of Service (DoS) condition.

A second improper privilege management vulnerability in the Juniper Networks Junos OS and Junos OS Evolved command-line interpreter (CLI) was also discovered, allowing a low-privileged user to overwrite local files as root, possibly leading to a system integrity issue or additional Denial of Service (DoS). Depending on the files overwritten, exploitation of this vulnerability could lead to a sustained Denial of Service (DoS) condition, requiring manual user intervention to recover.

Systems are only vulnerable if jdhcpd is running, which can be confirmed via the 'show system processes' command. For example:

root@host# run show system processes extensive | match dhcp
26537 root -16 0 97568K 13692K RUN 0 0:01 3.71% jdhcpd

These issues affect:

Juniper Networks Junos OS:

• All versions, including the following supported releases:
  • 15.1 versions prior to 15.1R7-S10;
  • 17.4 versions prior to 17.4R3-S5;
  • 18.3 versions prior to 18.3R3-S5;
  • 18.4 versions prior to 18.4R3-S9;
  • 19.1 versions prior to 19.1R3-S6;
  • 19.2 versions prior to 19.2R1-S7, 19.2R3-S3;
  • 19.3 versions prior to 19.3R2-S6, 19.3R3-S3;
  • 19.4 versions prior to 19.4R3-S6;
  • 20.1 versions prior to 20.1R2-S2, 20.1R3-S1;
  • 20.2 versions prior to 20.2R3-S2;
  • 20.3 versions prior to 20.3R3;
  • 20.4 versions prior to 20.4R2-S1, 20.4R3;
  • 21.1 versions prior to 21.1R1-S1, 21.1R2.

Juniper Networks Junos OS Evolved:

• All versions prior to 20.4R2-S3-EVO;
• All versions of 21.1-EVO.

There are several configuration options that enable DHCP service. For example:

[edit interfaces ... family inet dhcp]
[edit system processes dhcp-service]
[edit forwarding-options dhcp-relay]

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

This issue was discovered during external security research.

The following issues have been reported by the security researcher, and resolved in the releases listed:

The following software releases have been updated to resolve this specific issue:

Junos OS 15.1R7-S10, 17.4R3-S5, 18.3R3-S5, 18.4R3-S9, 19.1R3-S6, 19.2R1-S7, 19.2R3-S3, 19.3R2-S6, 19.3R3-S3, 19.4R3-S6, 20.1R2-S2, 20.1R3-S1, 20.2R3-S2, 20.3R3, 20.4R2-S1, 20.4R3, 21.1R1-S1, 21.1R2, 21.1R3, 21.2R1, and all subsequent releases.

Junos OS Evolved 20.4R2-S3-EVO, 21.2R1-EVO, and all subsequent releases.

This issue is being tracked as  1568654 .
 

Software releases or updates are available for download at https://support.juniper.net/support/downloads/
 

2021-10-13: Initial Publication.
2021-10-27: Added details on how to confirm whether jdhcpd is running.

• KB16613: Overview of the Juniper Networks SIRT Quarterly Security Bulletin Publication Process [juniper.net]
• KB16765: In which releases are vulnerabilities fixed? [juniper.net]
• KB16446: Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories [juniper.net]
• Report a Vulnerability - How to Contact the Juniper Networks Security Incident Response Team
• CVE-2021-31359: Local privilege escalation vulnerability in Juniper Networks Junos OS and Junos OS Evolved
• CVE-2021-31360: Improper privilege management vulnerability in the Juniper Networks Junos OS and Junos OS Evolved command-line interpreter

Juniper SIRT would like to acknowledge and thank Wenxu Yin (@awxylitol) of Alpha Lab, Qihoo 360 Technology Co. Ltd., for responsibly reporting this vulnerability.