CVE-2021-0239

Junos OS Evolved: Denial of Service due to receipt of specific genuine layer 2 frames.

MEDIUM
6.5
CVSS Score
Published: April 22, 2021 at 07:37 PM UTC
Updated: June 17, 2026 at 03:29 AM UTC
2 products affected across 2 vendorsJunos OS EvolvedJunos OS Evolved

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Severity
MEDIUM6.5
Exploit prediction
EPSS 0.4%

Description

In Juniper Networks Junos OS Evolved, receipt of a stream of specific genuine Layer 2 frames may cause the Advanced Forwarding Toolkit (AFT) manager process (Evo-aftmand), responsible for handling Route, Class-of-Service (CoS), Firewall operations within the packet forwarding engine (PFE) to crash and restart, leading to a Denial of Service (DoS) condition. By continuously sending this specific stream of genuine Layer 2 frames, an attacker can repeatedly crash the PFE, causing a sustained Denial of Service (DoS). This issue affects Juniper Networks Junos OS Evolved: All versions prior to 20.4R1-EVO. This issue does not affect Junos OS versions.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 20.4R1-EVO
Affected range stops below 20.4R1-EVO, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (1)

x_refsource_MISCVendor Advisory
https://kb.juniper.net/JSA11134

CVSS

6.5MEDIUMjuniper
Attack Vector
ADJACENT_NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-754

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