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2021-04 Security Bulletin: Junos OS: MX Series with MS-PIC, MS-SPC3, MS-MIC or MS-MPC: The BRAS Subscriber Services service activation portal is vulnerable to a Denial of Service (DoS) via malformed HTTP packets (CVE-2021-0251)

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Article ID: JSA11144 SECURITY_ADVISORIES Last Updated: 14 Apr 2021Version: 1.0
Product Affected:
This issue affects Junos OS 17.3, 17.4, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2, 19.3. Affected platforms: MX Series.
Problem:

A NULL Pointer Dereference vulnerability in the Captive Portal Content Delivery (CPCD) services daemon (cpcd) of Juniper Networks Junos OS on MX Series with

MS-PIC, MS-SPC3, MS-MIC or MS-MPC allows an attacker to send malformed HTTP packets to the device thereby causing a Denial of Service (DoS), crashing the Multiservices PIC Management Daemon (mspmand) process thereby denying users the ability to login, while concurrently impacting other mspmand services and traffic through the device.

Continued receipt and processing of these malformed packets will create a sustained Denial of Service (DoS) condition.

While the Services PIC is restarting, all PIC services will be bypassed until the Services PIC completes its boot process.

An attacker sending these malformed HTTP packets to the device who is not part of the Captive Portal experience is not able to exploit this issue.

This issue is not applicable to MX RE-based CPCD platforms.

This issue affects:

Juniper Networks Junos OS on MX Series:

  • 17.3 version 17.3R1 and later versions prior to 17.4 versions 17.4R2-S9, 17.4R3-S2;
  • 18.1 versions prior to 18.1R3-S9;
  • 18.2 versions prior to 18.2R3-S3;
  • 18.3 versions prior to 18.3R3-S1;
  • 18.4 versions prior to 18.4R3;
  • 19.1 versions prior to 19.1R2-S2, 19.1R3;
  • 19.2 versions prior to 19.2R2;
  • 19.3 versions prior to 19.3R3.
  • This issue does not affect Juniper Networks Junos OS versions prior to 17.3R1.

The subscriber management services with the captive portal must be enabled to be vulnerable to this issue.

Example locations:

[system services subscriber-management]
[services captive-portal-content-delivery]
[dynamic-profiles "profile-name" services]
[protocols ppp-service] - i.e. configured with subscriber management services.

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

This issue was seen during production usage.

This issue has been assigned CVE-2021-0251.

Solution:

The following software releases have been updated to resolve this specific issue: 17.4R2-S9, 17.4R3-S2, 18.1R3-S9, 18.2R3-S3, 18.3R3-S1, 18.4R3, 19.1R2-S2, 19.1R3, 19.2R2, 19.3R3, 19.4R1, and all subsequent releases.

This issue is being tracked as 1445812.

Workaround:
There are no viable workarounds for this issue other than disabling the captive portal services.
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:
8.6 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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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