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CVE-2021-0289

20
FAUCET Score

CVE-2021-0289 is a Time-of-check Time-of-use (TOCTOU) race condition vulnerability in Juniper Networks Junos OS, affecting various versions across multiple platforms (excluding Junos OS Evolved). When a user-defined ARP Policer is configured on Aggregated Ethernet (AE) interface units, this flaw allows an attacker to bypass it, replacing it with a default ARP policer. The vulnerability has a CVSS score of 5.3 (Medium), indicating an adjacent network attack vector with high attack complexity and a high 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
>= 5.7, < 15.1CPE matchmatch criteria
cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*
>= 15.2, < 18.4CPE matchmatch criteria
cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*
5.6CPE matchmatch criteria
cpe:2.3:o:juniper:junos:5.6:r1:*:*:*:*:*:*
18.4CPE matchmatch criteria
cpe:2.3:o:juniper:junos:18.4:-:*:*:*:*:*:*
18.4CPE matchmatch criteria
cpe:2.3:o:juniper:junos:18.4:r1:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

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

Attack Vector
ADJACENT_NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.26%
Probability of exploitation in next 30 days
EPSS Percentile
17.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0026 is in the 6th percentile among its peer group of 1,749 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.0 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 / JSA11191
Vendor Advisory