CVE-2021-31362: Junos OS and Junos OS Evolved: An IS-IS adjacency might be taken down if a bad hello PDU is received for an existing adjacency causing a DoS

Severity: low (CVSS 3.3 v2.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-10-19 · updated 2026-06-17
Weakness: CWE-693

Description

A Protection Mechanism Failure vulnerability in RPD (routing protocol daemon) of Juniper Networks Junos OS and Junos OS Evolved allows an adjacent unauthenticated attacker to cause established IS-IS adjacencies to go down by sending a spoofed hello PDU leading to a Denial of Service (DoS) condition. Continued receipted of these spoofed PDUs will create a sustained Denial of Service (DoS) condition. This issue affects: Juniper Networks Junos OS All 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-S7; 19.2 versions prior to 19.2R1-S7, 19.2R3-S3; 19.3 versions prior to 19.3R2-S6, 19.3R3-S2; 19.4 versions prior to 19.4R3-S3; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R3; 20.3 versions prior to 20.3R3; 20.4 versions prior to 20.4R2. Juniper Networks Junos OS Evolved All versions prior to 20.4R2-EVO; 21.1 versions prior to 21.1R2-EVO.

Affected products

Juniper Junos OS: through 18.1; 18.2, 18.2-r1, 18.2-r1-s2, 18.2-r1-s3, 18.2-r1-s4, 18.2-r1-s5 (+138)
Juniper Networks Junos OS Evolved: through 20.3; 20.4-r1, 20.4-r1-s1, 20.4-r1-s2, 21.1, 21.1-r1, 21.1-r1-s1

References

Get alerted when CVE-2021-31362 or the next vulnerability affects your stack