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.
Does this matter?
Lower severity and a low EPSS score (0.42%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.1
- 6.5 MEDIUMCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.42% probability · 36th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-252
- Affected
- juniper/junos
- Source
- sirt@juniper.net
EPSS 0.4% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://kb.juniper.net/JSA11228Patch, Vendor Advisory
- https://kb.juniper.net/JSA11228Patch, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.