Junos OS: MX Series: In subscriber management / BBE configuration authd can crash if a subscriber with a specific username tries to login leading to a DoS

Description

An Unchecked Return Value vulnerability in the authd (authentication daemon) of Juniper Networks Junos OS on MX Series configured for subscriber management / BBE allows an adjacent attacker to cause a crash by sending a specific username. This impacts authentication, authorization, and accounting (AAA) services on the MX devices and leads to a Denial of Service (DoS) condition. Continued receipted of these PPP login request will create a sustained Denial of Service (DoS) condition. This issue affects: Juniper Networks Junos OS 15.1 versions prior to 15.1R7-S9; 17.3 versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R3-S5; 18.1 versions prior to 18.1R3-S13; 18.2 versions prior to 18.2R3-S8; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R3-S9; 19.1 versions prior to 19.1R3-S6; 19.2 versions prior to 19.2R1-S7, 19.2R3-S3; 19.3 versions prior to 19.3R2-S6, 19.3R3-S3; 19.4 versions prior to 19.4R3-S3; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R3-S1; 20.3 versions prior to 20.3R3; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R2.

Scores

EPSS (exploitation in 30 days)

0.42% · top 64% of all CVEs (6 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.

Weakness

• CWE-252 (opens in a new tab)All about CWE-252 and its CVEs
• Denial of Service (DoS)

Affected products

• Juniper Networks · Junos OS

  • affected 15.1 – < 15.1R7-S9
  • affected 17.3 – < 17.3R3-S12
  • affected 17.4 – < 17.4R3-S5
  • affected 18.1 – < 18.1R3-S13
  • affected 18.2 – < 18.2R3-S8
  • affected 18.3 – < 18.3R3-S5
  • affected 18.4 – < 18.4R3-S9
  • affected 19.1 – < 19.1R3-S6
  • affected 19.2 – < 19.2R1-S7, 19.2R3-S3
  • affected 19.3 – < 19.3R2-S6, 19.3R3-S3
  • affected 19.4 – < 19.4R3-S3
  • affected 20.1 – < 20.1R3
  • affected 20.2 – < 20.2R3-S1
  • affected 20.3 – < 20.3R3
  • affected 20.4 – < 20.4R3
  • affected 21.1 – < 21.1R2

What to do

Solution: The following software releases have been updated to resolve this specific issue: 15.1R7-S9, 17.3R3-S12, 17.4R3-S5, 18.1R3-S13, 18.2R3-S8, 18.3R3-S5, 18.4R3-S9, 19.1R3-S6, 19.2R1-S7, 19.2R3-S3, 19.3R2-S6, 19.3R3-S3, 19.4R3-S3, 20.1R3, 20.2R3-S1, 20.3R3, 20.4R3, 21.1R2, 21.2R1, and all subsequent releases.

Workaround: Please always configure a domain map none: [access domain map none]

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

References (1)

• https://kb.juniper.net/JSA11228 (opens in a new tab)x_refsource_CONFIRMx_transferred

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2021-31366](https://trackcve.app/badge/CVE-2021-31366.svg)](https://trackcve.app/cve/CVE-2021-31366)

Record last updated 17 Sept 2024, 04:25 UTC.