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2021-10 Security Bulletin: Junos OS: When using J-Web with HTTP an attacker may retrieve encryption keys via Person-in-the-Middle attacks. (CVE-2021-31386)

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Article ID: JSA11254 SECURITY_ADVISORIES Last Updated: 13 Oct 2021Version: 2.0
Product Affected:
This issue affects Junos OS 12.3, 15.1, 18.3, 18.4, 19.1, 19.2, 19.3, 19.4, 20.1, 20.2, 20.3, 20.4, 21.1, 21.2.
Problem:

A Protection Mechanism Failure vulnerability in the J-Web HTTP service of Juniper Networks Junos OS allows a remote unauthenticated attacker to perform Person-in-the-Middle (PitM) attacks against the device.

This issue affects:

Juniper Networks Junos OS

  • 12.3 versions prior to 12.3R12-S20;
  • 15.1 versions prior to 15.1R7-S11;
  • 18.3 versions prior to 18.3R3-S6;
  • 18.4 versions prior to 18.4R3-S10;
  • 19.1 versions prior to 19.1R3-S7;
  • 19.2 versions prior to 19.2R3-S4;
  • 19.3 versions prior to 19.3R3-S4;
  • 19.4 versions prior to 19.4R3-S6;
  • 20.1 versions prior to 20.1R3-S2;
  • 20.2 versions prior to 20.2R3-S3;
  • 20.3 versions prior to 20.3R3-S1;
  • 20.4 versions prior to 20.4R3;
  • 21.1 versions prior to 21.1R3;
  • 21.2 versions prior to 21.2R2.

The device must have J-Web's HTTP services enabled to be susceptible to this issue:

[system services web-management http]

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-2021-31386.

Solution:

The following software releases have been updated to resolve this specific issue: 12.3R12-S20, 15.1R7-S11, 18.3R3-S6, 18.4R3-S10, 19.1R3-S7, 19.2R3-S4, 19.3R3-S4, 19.4R3-S6, 20.1R3-S2, 20.2R3-S3, 20.3R3-S1, 20.4R3, 21.1R3, 21.2R2, 21.3R1, and all subsequent releases.

Note: Use of HTTP must also be discontinued.

This issue is being tracked as 1603199.

Workaround:

Discontinue the use of HTTP, instead use HTTPS when using J-Web.

[system services web-management https]
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:
5.3 (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N)
Severity Level:
Medium
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:
Andy Coles of Microsoft MSRC Vulnerabilities and Mitigations Team

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