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CVE-2021-0243

18
FAUCET Score

CVE-2021-0243 describes an Improper Handling of Unexpected Data vulnerability in the firewall policer of Juniper Networks Junos OS on EX4300 switches, specifically affecting IPv4 traffic. This flaw allows traffic to bypass configured policer limits on Layer 2 ports, potentially leading to a limited Denial of Service (DoS) condition. The vulnerability has a CVSS v3.1 score of 4.7 (Medium), indicating an attack vector of Adjacent Network, low attack complexity, and a low impact on availability. There is no evidence of active exploitation, publicly available exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 17.3R3-S10CPE match
cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*
>= 17.4, < 17.4R3-S3CPE match
cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*
>= 18.1, < 18.1R3-S11CPE match
cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*
>= 18.2, < 18.2R3-S6CPE match
cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*
>= 18.3, < 18.3R3-S4CPE match
cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

4.7MEDIUM

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L

Attack Vector
ADJACENT_NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
LOW
Exploitability Score
2.8
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.38%
Probability of exploitation in next 30 days
EPSS Percentile
30.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0038 is in the 45th percentile among its peer group of 1,802 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (1)

junipervendor investigatingvia nvd_reference
View patch

References

kb.juniper.net / JSA11136
Vendor Advisory