What’s Vulnerable › Vulnerabilities

CVE-2021-0239: Junos OS Evolved: Denial of Service due to receipt of specific genuine layer 2 frames.

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-04-22 · updated 2026-06-17
• Weakness: CWE-754

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 products

• Juniper Networks Junos OS Evolved: 20.4-r1

References

• https://kb.juniper.net/JSA11134
• https://kb.juniper.net/JSA11134

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