CVE-2021-0233 | Junos OS: ACX500 Series, ACX4000 Series: Denial of Service due to FFEB crash while processing high rate of specific packets.

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.

Published: 2021-04-22 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-0233 is rated Moderate Risk (53.5/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.54%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-0233

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-11-21 0.39% 0.54% +0.15%
2 2025-11-18 0.54% 0.39% -0.15%
3 2025-03-30 — 0.54% —

Full EPSS history (10 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-0233

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-0233

Affected software / configurations for CVE-2021-0233

Vendor Product Version Raw CPE
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:-:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r1:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r1-s1:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r1-s2:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r1-s3:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r1-s4:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r1-s5:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r1-s6:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r1-s7:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r2:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r2-s1:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r2-s10:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r2-s11:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r2-s2:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r2-s3:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r2-s4:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r2-s5:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r2-s6:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r2-s7:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r2-s8:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r2-s9:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r3:*:*:*:*:*:*
juniper junos 17.4 cpe:2.3:o:juniper:junos:17.4:r3-s1:*:*:*:*:*:*

References for CVE-2021-0233

URL Tags
https://kb.juniper.net/JSA11128 Vendor Advisory
cvelogic Threat Intelligence