Junos OS: J-Web allows a locally authenticated attacker to escalate their privileges to root.

Description

An Improper Input Validation vulnerability in J-Web of Juniper Networks Junos OS allows a locally authenticated J-Web attacker to escalate their privileges to root over the target device. This issue affects: Juniper Networks Junos OS All 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 19.2R3-S3; 19.3 versions prior to 19.3R3-S3; 19.4 versions prior to 19.4R3-S5; 20.1 versions prior to 20.1R3-S1; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3-S1; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R2, 21.1R3; 21.2 versions prior to 21.2R1-S1, 21.2R2;

Scores

EPSS (exploitation in 30 days)

1.2% · top 31% of all CVEs (6 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.8.

Weakness

• CWE-20 Improper Input Validation (opens in a new tab)All about CWE-20 and its CVEs
• Privilege Escalation

Affected products

• Juniper Networks · Junos OS

  • affected unspecified – < 18.3R3-S5
  • affected 18.4 – < 18.4R3-S9
  • affected 19.1 – < 19.1R3-S6
  • affected 19.2 – < 19.2R3-S3
  • affected 19.3 – < 19.3R3-S3
  • affected 19.4 – < 19.4R3-S5
  • affected 20.1 – < 20.1R3-S1
  • affected 20.2 – < 20.2R3-S2
  • affected 20.3 – < 20.3R3-S1
  • affected 20.4 – < 20.4R3
  • affected 21.1 – < 21.1R2, 21.1R3
  • affected 21.2 – < 21.2R1-S1, 21.2R2

What to do

Solution: The following software releases have been updated to resolve this specific issue: 18.3R3-S5, 18.4R3-S9, 19.1R3-S6, 19.2R3-S3, 19.3R3-S3, 19.4R3-S5, 20.1R3-S1, 20.2R3-S2, 20.3R3-S1, 20.4R3, 21.1R2, 21.1R3, 21.2R1-S1, 21.2R2, 21.3R1, and all subsequent releases.

Workaround: To reduce the risk of exploitation of this issue, use access lists or firewall filters to limit access to only trusted administrative networks, hosts and users. Alternatively, J-Web can be disabled.

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

References (1)

• https://kb.juniper.net/JSA11237 (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-2021-31372](https://trackcve.app/badge/CVE-2021-31372.svg)](https://trackcve.app/cve/CVE-2021-31372)

Record last updated 16 Sept 2024, 20:47 UTC.