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2021-04 Security Bulletin: Junos OS: J-Web can be compromised through reflected client-side HTTP parameter pollution attacks. (CVE-2021-0269)

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Article ID: JSA11160 SECURITY_ADVISORIES Last Updated: 14 Apr 2021Version: 1.0
Product Affected:
This issue affects Junos OS all releases prior to 17.4R3-S3, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2, 19.3, 19.4, 20.1, 20.2.
Problem:

The improper handling of client-side parameters in J-Web of Juniper Networks Junos OS allows an attacker to perform a number of different malicious actions against a target device when a user is authenticated to J-Web. An attacker may be able to supersede existing parameters, including hardcoded parameters within the HTTP/S session, access and exploit variables, bypass web application firewall rules or input validation mechanisms, and otherwise alter and modify J-Web's normal behavior. An attacker may be able to transition victims to malicious web services, or exfiltrate sensitive information from otherwise secure web forms.

This issue affects:

Juniper Networks Junos OS:

  • All versions prior to 17.4R3-S3;
  • 18.1 versions prior to 18.1R3-S12;
  • 18.2 versions prior to 18.2R3-S6;
  • 18.3 versions prior to 18.3R3-S4;
  • 18.4 versions prior to 18.4R3-S6;
  • 19.1 versions prior to 19.1R3-S4;
  • 19.2 versions prior to 19.2R3-S1;
  • 19.3 versions prior to 19.3R3-S1;
  • 19.4 versions prior to 19.4R2-S2, 19.4R3;
  • 20.1 versions prior to 20.1R2;
  • 20.2 versions prior to 20.2R2.

This issue requires J-Web to be enabled on the device.

The examples of the config stanza affected by this issue:

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

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

This issue was found during internal product security testing or research.

This issue has been assigned CVE-2021-0269.

Solution:

The following software releases have been updated to resolve this specific issue: 17.4R3-S3, 18.1R3-S12, 18.2R3-S6, 18.3R3-S4, 18.4R3-S6, 19.1R3-S4, 19.2R3-S1, 19.3R3-S1, 19.4R2-S2, 19.4R3, 20.1R2, 20.2R2, 20.3R1, and all subsequent releases.

This issue is being tracked as 1501588.

Workaround:

To reduce the risk of exploitation utilize common security BCPs to limit the exploitable surface by limiting access to network and device to trusted systems, administrators, networks and hosts.

Access the J-Web service from trusted hosts which may not be compromised by cross-site scripting attacks, for example, deploying jump hosts with no internet access.

Alternatively, disable J-Web.

Implementation:
Software releases or updates are available for download at https://support.juniper.net/support/downloads/
Modification History:
2021-04-14: Initial Publication.
CVSS Score:
8.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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."

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