CVE-2021-0203 | Junos OS: EX and QFX5K Series: Storm Control does not work as expected when Redundant Trunk Group is configured

On Juniper Networks EX and QFX5K Series platforms configured with Redundant Trunk Group (RTG), Storm Control profile applied on the RTG interface might not take affect when it reaches the threshold condition. Storm Control enables the device to monitor traffic levels and to drop broadcast, multicast, and unknown unicast packets when a specified traffic level is exceeded, thus preventing packets from proliferating and degrading the LAN. Note: this issue does not affect EX2200, EX3300, EX4200, and EX9200 Series. This issue affects Juniper Networks Junos OS on EX Series and QFX5K Series: 15.1 versions prior to 15.1R7-S7; 16.1 versions prior to 16.1R7-S8; 17.2 versions prior to 17.2R3-S4; 17.3 versions prior to 17.3R3-S8; 17.4 versions prior to 17.4R2-S11, 17.4R3-S2; 18.1 versions prior to 18.1R3-S10; 18.2 versions prior to 18.2R3-S5; 18.3 versions prior to 18.3R2-S4, 18.3R3-S2; 18.4 versions prior to 18.4R2-S5, 18.4R3-S3; 19.1 versions prior to 19.1R2-S2, 19.1R3-S2; 19.2 versions prior to 19.2R1-S5, 19.2R2-S1, 19.2R3; 19.3 versions prior to 19.3R2-S4, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2-S1, 19.4R3; 20.1 versions prior to 20.1R1-S2, 20.1R2.

Published: 2021-01-15 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-0203 is rated Moderate Risk (55.4/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.00%). 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-2021-0203

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 2026-06-15 0.39% 1.00% +0.61%
2 2025-03-30 0.46% 0.39% -0.08%
3 2025-03-29 — 0.46% —

Full EPSS history (9 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-0203

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.6 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
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 4.0 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/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:M)
Exploitation needs some favorable conditions, but not exceptional ones.
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.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2021-0203

Affected software / configurations for CVE-2021-0203

Vendor Product Version Raw CPE
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:-:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:a1:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f1:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f2:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f2-s1:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f2-s2:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f2-s3:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f2-s4:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f3:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f4:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f5:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f5-s7:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f6:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f6-s1:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f6-s12:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f6-s2:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f6-s3:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f6-s4:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f6-s7:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:f7:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r1:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r2:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r3:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r4:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r4-s7:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r4-s8:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r4-s9:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r5:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r5-s1:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r5-s5:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r5-s6:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r6:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r6-s1:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r6-s2:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r6-s6:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r7:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r7-s1:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r7-s2:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r7-s3:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r7-s4:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r7-s5:*:*:*:*:*:*
juniper junos 15.1 cpe:2.3:o:juniper:junos:15.1:r7-s6:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:-:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r1:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r2:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r3:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r3-s10:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r3-s11:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r4:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r4-s12:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r4-s2:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r4-s3:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r4-s4:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r4-s6:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r5:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r5-s4:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r6-s1:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r6-s6:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r7:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r7-s2:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r7-s3:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r7-s4:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r7-s5:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r7-s6:*:*:*:*:*:*
juniper junos 16.1 cpe:2.3:o:juniper:junos:16.1:r7-s7:*:*:*:*:*:*
juniper junos 17.2 cpe:2.3:o:juniper:junos:17.2:-:*:*:*:*:*:*
juniper junos 17.2 cpe:2.3:o:juniper:junos:17.2:r1:*:*:*:*:*:*
juniper junos 17.2 cpe:2.3:o:juniper:junos:17.2:r1-s1:*:*:*:*:*:*
juniper junos 17.2 cpe:2.3:o:juniper:junos:17.2:r1-s2:*:*:*:*:*:*
juniper junos 17.2 cpe:2.3:o:juniper:junos:17.2:r1-s3:*:*:*:*:*:*
juniper junos 17.2 cpe:2.3:o:juniper:junos:17.2:r1-s4:*:*:*:*:*:*
juniper junos 17.2 cpe:2.3:o:juniper:junos:17.2:r1-s5:*:*:*:*:*:*
juniper junos 17.2 cpe:2.3:o:juniper:junos:17.2:r1-s7:*:*:*:*:*:*
juniper junos 17.2 cpe:2.3:o:juniper:junos:17.2:r1-s8:*:*:*:*:*:*
juniper junos 17.2 cpe:2.3:o:juniper:junos:17.2:r2:*:*:*:*:*:*
juniper junos 17.2 cpe:2.3:o:juniper:junos:17.2:r2-s11:*:*:*:*:*:*
juniper junos 17.2 cpe:2.3:o:juniper:junos:17.2:r2-s6:*:*:*:*:*:*
juniper junos 17.2 cpe:2.3:o:juniper:junos:17.2:r2-s7:*:*:*:*:*:*
juniper junos 17.2 cpe:2.3:o:juniper:junos:17.2:r3-s1:*:*:*:*:*:*

References for CVE-2021-0203

URL Tags
https://kb.juniper.net/JSA11093 Vendor Advisory
cvelogic Threat Intelligence