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2021-10 Security Bulletin: Junos OS: J-Web allows a locally authenticated attacker to escalate their privileges to root (CVE-2021-31372)

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Article ID: JSA11237 SECURITY_ADVISORIES Last Updated: 13 Oct 2021Version: 1.0
Product Affected:
This issue affects Junos OS all versions prior to 18.3R3-S5, 18.4, 19.1, 19.2, 19.3, 19.4, 20.1, 20.2, 20.3, 20.4, 21.1, 21.2.
Problem:

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;

The examples of the config stanza affected by this issue:

[system services web-management]
[system services web-management https]

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

This issue was discovered during external security research.

This issue has been assigned CVE-2021-31372.

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.

This issue is being tracked as 1594516.

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.

Implementation:
Software releases or updates are available for download at https://support.juniper.net/support/downloads/
Modification History:
2021-10-13: Initial Publication.
CVSS Score:
8.8 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
Severity Level:
High
Severity Assessment:
Information for how Juniper Networks uses CVSS can be found at KB 16446 "Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."
Acknowledgements:
The Juniper SIRT would like to acknowledge and thank Andy Coles of Microsoft MSRC Vulnerabilities and Mitigations Team.

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