CVE-2021-31366

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.

• CWE-252
• CWE-252

• https://kb.juniper.net/JSA11228Patch, Vendor Advisory
• https://kb.juniper.net/JSA11228Patch, Vendor Advisory

Published

Oct 19, 2021

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2021-31360An improper privilege management vulnerability in the Junipe…7.1
• CVE-2021-31361An Improper Check for Unusual or Exceptional Conditions vuln…5.3
• CVE-2021-31362A Protection Mechanism Failure vulnerability in RPD (routing…6.5
• CVE-2021-31363In an MPLS P2MP environment a Loop with Unreachable Exit Con…6.5
• CVE-2021-31364An Improper Check for Unusual or Exceptional Conditions vuln…5.9
• CVE-2021-31365An Uncontrolled Resource Consumption vulnerability in Junipe…6.5
• CVE-2021-31367A Missing Release of Memory after Effective Lifetime vulnera…6.5
• CVE-2021-31368An Uncontrolled Resource Consumption vulnerability in the ke…7.5
• CVE-2021-31369On MX Series platforms with MS-MPC/MS-MIC, an Allocation of …5.3
• CVE-2021-3137XWiki 12.10.2 allows XSS via an SVG document to the upload f…5.4
• CVE-2021-31370An Incomplete List of Disallowed Inputs vulnerability in Pac…6.5
• CVE-2021-31371Juniper Networks Junos OS uses the 128.0.0.0/2 subnet for in…5.3