CVE-2021-0239 Junos OS Evolved: Denial of Service due to receipt of specific genuine layer 2 frames.
An attacker can cause a sustained Denial of Service by sending specific Layer 2 frames that crash the packet forwarding engine in Junos OS Evolved.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2021-0239?
CVE-2021-0239 is a medium-severity denial of service vulnerability in Juniper Junos Os Evolved, published on 22 Apr 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Weakness: CWE-754
Which versions are affected by CVE-2021-0239?
It affects 1 product.
Products include Juniper Junos Os Evolved.
How do I fix CVE-2021-0239?
No fix has been published for CVE-2021-0239 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2021-0239 being exploited?
There is no known exploitation of CVE-2021-0239 in the wild and no public exploit code.
Other vulnerabilities in Juniper Junos Os Evolved
- CVE-2026-21902 Junos OS Evolved: PTX Series: A vulnerability allows a unauthenticated, network-based attacker to execute code as root
- CVE-2023-28983 Junos OS Evolved: Shell Injection vulnerability in the gNOI server
- CVE-2025-21599 Denial of service in Junos OS Evolved
- CVE-2024-47502 Junos OS Evolved: TCP session state is not always cleared on the Routing Engine leading to DoS
- CVE-2024-39531 Junos OS Evolved: ACX 7000 Series: Protocol specific DDoS configuration affects other protocols
Sources
Also known as GHSA-hr3q-mvqf-hmmc.