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Fencer Vulns
high 7.5

CVE-2021-31376 json

Junos OS: ACX Series: Packet Forwarding Engine manager (FXPC) process crashes when processing DHCPv6 packets

published 2021-10-19 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-18286

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.0%
EPSS 1.0% chance of exploitation in 30 days, percentile 63%
public exploits
0
none known

Summary

An Improper Input Validation vulnerability in Packet Forwarding Engine manager (FXPC) process of Juniper Networks Junos OS allows an attacker to cause a Denial of Service (DoS) by sending specific DHCPv6 packets to the device and crashing the FXPC service. Continued receipt and processing of this specific packet will create a sustained Denial of Service (DoS) condition. This issue affects only the following platforms in ACX Series: ACX500, ACX1000, ACX1100, ACX2100, ACX2200, ACX4000, ACX5048, ACX5096 devices. Other ACX platforms are not affected from this issue. This issue affects Juniper Networks Junos OS on ACX500, ACX1000, ACX1100, ACX2100, ACX2200, ACX4000, ACX5048, ACX5096: 18.4 version 18.4R3-S7 and later versions prior to 18.4R3-S8. This issue does not affect: Juniper Networks Junos OS 18.4 versions prior to 18.4R3-S7 on ACX500, ACX1000, ACX1100, ACX2100, ACX2200, ACX4000, ACX5048, ACX5096.

Exploit prediction

1.02% chance of exploitation in the next 30 days, higher than 63% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P

Affected products

  • Juniper Networks Junos OS

Classification

Weakness
  • CWE-20 Improper Input Validation

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.