CVE-2021-0254 : Exploit Details and Defense Strategies
Learn about CVE-2021-0254, a critical vulnerability in Juniper Networks Junos OS that allows remote attackers to trigger a Denial of Service or execute remote code.
A buffer size validation vulnerability in the overlayd service of Juniper Networks Junos OS may allow an unauthenticated remote attacker to send specially crafted packets to the device, triggering a partial Denial of Service (DoS) condition or leading to remote code execution (RCE).
Understanding CVE-2021-0254
This CVE relates to a critical vulnerability in Junos OS discovered on April 14, 2021.
What is CVE-2021-0254?
This vulnerability in Juniper Networks Junos OS allows unauthenticated attackers to exploit a buffer size validation issue in the overlayd service, potentially causing a partial DoS or remote code execution.
The Impact of CVE-2021-0254
The issue can have a critical impact, with a CVSS base score of 9.8 (Critical). Attackers can exploit the vulnerability to disrupt services or execute arbitrary code remotely.
Technical Details of CVE-2021-0254
The vulnerability arises from improper buffer size validation in the overlayd service, affecting several versions of Junos OS.
Vulnerability Description
The overlayd service, responsible for handling Overlay OAM packets, lacks proper buffer size validation, leading to a buffer overflow, which can be exploited by unauthenticated attackers.
Affected Systems and Versions
Juniper Networks Junos OS versions prior to specific releases are vulnerable, including MX Series, ACX Series, and QFX Series platforms with a Virtual Extensible LAN overlay network configuration.
Exploitation Mechanism
Attackers can send specially crafted packets to exploit the buffer overflow, potentially achieving remote code execution.
Mitigation and Prevention
It's crucial to take immediate steps to secure affected systems and prevent exploitation of CVE-2021-0254.
Immediate Steps to Take
Limit access to the device via UDP to trusted administrative networks, or disable Overlay OAM packet through specific configuration commands.
Long-Term Security Practices
Regularly update Junos OS to the latest patched versions and enforce network segmentation and access controls to mitigate risks.
Patching and Updates
Ensure that the affected Junos OS versions are updated to the software releases specified to resolve the vulnerability. Proactive fixes are also available for releases that may not be directly affected.