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2021-07 Security Bulletin: Junos OS: J-Web allows a locally authenticated attacker to escalate their privileges to root. (CVE-2021-0278)



Article ID: JSA11182 SECURITY_ADVISORIES Last Updated: 14 Jul 2021Version: 2.0
Product Affected:
This issue affects Junos OS 19.3, 19.4, 20.1, 20.2, 20.3, 20.4, 21.1.

An Improper Input Validation vulnerability in J-Web of Juniper Networks Junos OS allows a locally authenticated attacker to escalate their privileges to root over the target device.

junos:18.3R3-S5 junos:18.4R3-S9 junos:19.1R3-S6 junos:19.3R2-S6 junos:19.3R3-S3 junos:19.4R1-S4 junos:19.4R3-S4 junos:20.1R2-S2 junos:20.1R3 junos:20.2R3-S1 junos:20.3X75-D20 junos:20.3X75-D30 junos:20.4R2-S1 junos:20.4R3 junos:21.1R1-S1 junos:21.1R2 junos:21.2R1 junos:21.3R1

This issue affects:

Juniper Networks Junos OS

19.3 versions 19.3R1 and above prior to 19.3R2-S6, 19.3R3-S3;

19.4 versions prior to 19.4R3-S5;

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.

This issue does not affect Juniper Networks Junos OS versions prior to 19.3R1.

The following minimal configuration is necessary:

[system services web-management http]


[system services web-management https]

Juniper SIRT is not aware of any malicious exploitation of this vulnerability. However, a proof-of-concept exploit does exist in the wild.

This issue was seen during production usage.

This issue has been assigned CVE-2021-0278.


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

In addition to the above fixed releases, for the following not-affected releases additional security enhancements were included in Junos OS 18.3R3-S5, 18.4R3-S9, 19.1R3-S6 as a result of resolving this issue.

This issue is being tracked as 1592021 and 1511853.


There are no viable workarounds for this issue other than disabling J-Web.

To reduce the risk of exploitation of these issues, use access lists or firewall filters to limit access to only trusted administrative networks, hosts and users.

Software releases or updates are available for download at
Modification History:
2021-07-14: 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:
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."
The Juniper SIRT wishes to thank Luca Ercoli regarding PR 1511853

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