Junos OS and Junos OS Evolved: Denial of Service vulnerability in local file processing

Description

An improper privilege management vulnerability in the Juniper Networks Junos OS and Junos OS Evolved command-line interpreter (CLI) allows a low-privileged user to overwrite local files as root, possibly leading to a system integrity issue or 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 This issue affects: 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.

Timeline

Scores

EPSS (exploitation in 30 days)

0.21% · top 89% of all CVEs (7 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.1.

Weakness

• CWE-269 Improper Privilege Management (opens in a new tab)All about CWE-269 and its CVEs
• CWE-20 Improper Input Validation (opens in a new tab)All about CWE-20 and its CVEs
• Denial of Service (DoS)

Affected products

• Juniper Networks · Junos OS

  • affected 15.1 – < 15.1R7-S10
  • affected 17.4 – < 17.4R3-S5
  • affected 18.3 – < 18.3R3-S5
  • affected 18.4 – < 18.4R3-S9
  • affected 19.1 – < 19.1R3-S6
  • affected 19.2 – < 19.2R1-S7, 19.2R3-S3
  • affected 19.3 – < 19.3R2-S6, 19.3R3-S3
  • affected 19.4 – < 19.4R3-S6
  • affected 20.1 – < 20.1R2-S2, 20.1R3-S1
  • affected 20.2 – < 20.2R3-S2
  • affected 20.3 – < 20.3R3
  • affected 20.4 – < 20.4R2-S1, 20.4R3
  • affected 21.1 – < 21.1R1-S1, 21.1R2

• Juniper Networks · Junos OS Evolved

  • affected unspecified – < 20.4R2-S3-EVO
  • affected 21.1R1-EVO – < 21.1*

What to do

Solution: 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.

Workaround: Use access lists or firewall filters to limit access to the device via CLI only from trusted hosts and from trusted administrators.

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

References (1)

• https://kb.juniper.net/JSA11222 (opens in a new tab)x_refsource_CONFIRMx_transferred

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2021-31360](https://trackcve.app/badge/CVE-2021-31360.svg)](https://trackcve.app/cve/CVE-2021-31360)

Record last updated 17 Sept 2024, 01:31 UTC.