Junos OS: ACX500 Series, ACX4000 Series: Denial of Service due to FFEB crash while processing high rate of specific packets.

published 2021-04-22 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-2852

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 61%
public exploits: 0; none known

A vulnerability in Juniper Networks Junos OS ACX500 Series, ACX4000 Series, may allow an attacker to cause a Denial of Service (DoS) by sending a high rate of specific packets to the device, resulting in a Forwarding Engine Board (FFEB) crash. Continued receipt of these packets will sustain the Denial of Service (DoS) condition. This issue affects Juniper Networks Junos OS on ACX500 Series, ACX4000 Series: 17.4 versions prior to 17.4R3-S2.

Patch / fix

fixed in 1

Juniper Networks Junos OS 17.4R3-S2

Exploit prediction

0.96% chance of exploitation in the next 30 days, higher than 61% 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-794 Incomplete Filtering of Multiple Instances of Special Elements
CWE-400 Uncontrolled Resource Consumption

References

kb.juniper.net /JSA11128
vendor-advisory

Sources

CVE List CVE-2021-0233
NVD CVE-2021-0233

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Summary