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2021-04 Security Bulletin: Junos OS: Denial of Service vulnerability in J-Web and web based (HTTP/HTTPS) services caused by a high number of specific requests (CVE-2021-0261)

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Article ID: JSA11152 SECURITY_ADVISORIES Last Updated: 14 Apr 2021Version: 2.0
Product Affected:
This issue affects Junos OS 12.3, 12.3X48, 15.1, 15.1X49, 16.1, 17.3, 17.4, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2, 19.3, 19.4, 20.1, 20.2.
Problem:

A vulnerability in the HTTP/HTTPS service used by J-Web, Web Authentication, Dynamic-VPN (DVPN), Firewall Authentication Pass-Through with Web-Redirect, and Captive Portal allows an unauthenticated attacker to cause an extended Denial of Service (DoS) for these services by sending a high number of specific requests.

This issue affects:

Juniper Networks Junos OS:

  • 12.3 versions prior to 12.3R12-S17 on EX Series;
  • 12.3X48 versions prior to 12.3X48-D105 on SRX Series;
  • 15.1 versions prior to 15.1R7-S8;
  • 15.1X49 versions prior to 15.1X49-D230 on SRX Series;
  • 16.1 versions prior to 16.1R7-S8;
  • 17.3 versions prior to 17.3R3-S10;
  • 17.4 versions prior to 17.4R2-S12, 17.4R3-S3;
  • 18.1 versions prior to 18.1R3-S11;
  • 18.2 versions prior to 18.2R3-S6;
  • 18.3 versions prior to 18.3R2-S4, 18.3R3-S3;
  • 18.4 versions prior to 18.4R2-S5, 18.4R3-S4;
  • 19.1 versions prior to 19.1R2-S2, 19.1R3-S2;
  • 19.2 versions prior to 19.2R1-S5, 19.2R3;
  • 19.3 versions prior to 19.3R2-S4, 19.3R3;
  • 19.4 versions prior to 19.4R1-S3, 19.4R2-S2, 19.4R3;
  • 20.1 versions prior to 20.1R1-S3, 20.1R2;
  • 20.2 versions prior to 20.2R1-S1, 20.2R2.

The following are examples of the config stanzas that use the web-service that are vulnerable to this issue:

[system services web-management http]
[system services web-management https]
[services captive-portal secure-authentication]
[security dynamic-vpn] in combination with clients using https://<srx-ip>/(dynamic-vpn) to establish the vpn
[access firewall-authentication web-authentication] in combination with [security policies ... then permit firewall-authentication web-authentication client-match ...]
[access firewall-authentication pass-through http] in combination with [security policies ... then permit firewall-authentication pass-through web-redirect]

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-2021-0261.

Solution:

The following software releases have been updated to resolve this specific issue: 12.3R12-S17, 12.3X48-D105, 15.1R7-S8, 15.1X49-D230, 16.1R7-S8, 17.3R3-S10, 17.4R2-S12, 17.4R3-S3, 18.1R3-S11, 18.2R3-S6, 18.3R2-S4, 18.3R3-S3, 18.4R2-S5, 18.4R3-S4, 19.1R2-S2, 19.1R3-S2, 19.2R1-S5, 19.2R3, 19.3R2-S4, 19.3R3, 19.4R1-S3, 19.4R2-S2, 19.4R3, 20.1R1-S3, 20.1R2, 20.2R1-S1, 20.2R2, 20.3R1, and all subsequent releases.

This issue is being tracked as 1513887.

Workaround:

There are no viable workarounds for this issue other than disabling the web-service:
[deactivate system services web-management]

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.

The 'restart web-management' command can be used to restart the web-service to recover from this issue.

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:
7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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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