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Fencer Vulns
medium 6.5

CVE-2021-31370 json

Junos OS: QFX5000 Series and EX4600 Series: Control traffic might be dropped if a high rate of specific multicast traffic is received

published 2021-10-19 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-18280

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 36%
public exploits
0
none known

Summary

An Incomplete List of Disallowed Inputs vulnerability in Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on QFX5000 Series and EX4600 Series allows an adjacent unauthenticated attacker which sends a high rate of specific multicast traffic to cause control traffic received from the network to be dropped. This will impact control protocols (including but not limited to routing-protocols) and lead to a Denial of Service (DoS). Continued receipt of this specific multicast traffic will create a sustained Denial of Service (DoS) condition. This issue affects Juniper Networks Junos OS on QFX5000 and EX4600 Series: All versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R3-S5; 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 19.4R1-S4, 19.4R3-S3; 20.1 versions prior to 20.1R2-S2, 20.1R3-S1; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3; 20.4 versions prior to 20.4R2-S2, 20.4R3; 21.1 versions prior to 21.1R1-S1, 21.1R2.

Patch / fix

  • Juniper Networks Junos OS 17.3R3-S12, 17.4R3-S5, 18.3R3-S5, 18.4R3-S9, 19.1R3-S6, 19.2R1-S7, 19.2R3-S3, 19.3R2-S6, 19.3R3-S3, 19.4R1-S4, 19.4R3-S3, 20.1R2-S2, 20.1R3-S1, 20.2R3-S2, 20.3R3, 20.4R2-S2, 20.4R3, 21.1R1-S1, 21.1R2

Exploit prediction

0.42% chance of exploitation in the next 30 days, higher than 36% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 6.5 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 3.3 AV:A/AC:L/Au:N/C:N/I:N/A:P

Affected products

  • Juniper Networks Junos OS

Classification

Weakness
  • CWE-184 Incomplete List of Disallowed Inputs

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.