CVE-2021-0291Network attack vector

Service degradation via externally exposed AgentX listener

Published Jul 15, 2021 · Updated Sep 16, 2024

Exposure of system data in Junos OS and Junos OS Evolved allows remote attackers to degrade routing-engine service through TCP port 705. The AgentX process incorrectly accepts external connections instead of restricting its TCP/705 listener to the internal routing instance. Exploitation requires a high rate of specific unauthenticated network traffic, significantly raising Routing Engine CPU use and causing a partial service interruption.

CVSS severity6.5
Medium
EPSS probability1.01%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Exposure of system data in Junos OS and Junos OS Evolved allows remote attackers to degrade routing-engine service through TCP port 705. The AgentX process incorrectly accepts external connections instead of restricting its TCP/705 listener to the internal routing instance. Exploitation requires a high rate of specific unauthenticated network traffic, significantly raising Routing Engine CPU use and causing a partial service interruption.

The record

CVE
CVE-2021-0291
Published
Jul 15, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS Evolved
Classifications
CWE-200, CWE-497, T1498
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <20.3R2-EVO

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OS Evolvedversion=unspecified <20.3R2-EVO
Juniper Networks · Junos OSversion=15.1 <15.1R7-S9; version=17.3 <17.3R3-S12; version=17.4 <17.4R2-S13, 17.4R3-S5; version=18.3 <18.3R3-S5; version=18.4 <18.4R2-S8, 18.4R3-S9; version=19.1 <19.1R3-S5; version=19.2 <19.2R3-S2; version=19.3 <19.3R2-S6, 19.3R3-S2; version=19.4 <19.4R1-S4, 19.4R2-S4, 19.4R3; version=20.1 <20.1R2; version=20.2 <20.2R2; version=20.3 <20.3R2

Published CVSS scores

6.4NIST NVDAV:N/AC:L/Au:N/C:P/I:N/A:P
6.5Juniper NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-200Exposure of Sensitive Information to an Unauthorized Actor
CWE-497Exposure of Sensitive System Information to an Unauthorized Control Sphere
T1498Network Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo