What is CVE-2020-1350?
CVE-2020-1350, also known as “SIGRed,” is a critical remote code execution vulnerability found in the Windows Domain Name System (DNS) server. This vulnerability allows remote attackers to execute arbitrary code on the affected server by sending specially crafted DNS queries. It affects multiple versions of Windows Server, posing a severe threat to organizations that rely on these servers for DNS and network management.
CVSS Score and Severity
- CVSS Score: 10.0 (Critical)
- Severity: The CVSS score of 10.0 out of 10 reflects the critical nature of this vulnerability. The potential for remote code execution without authentication makes this a severe issue for organizations using Windows Server for DNS services.
So what’s the problem?
CVE-2020-1350 is particularly dangerous because it allows attackers to take full control of the affected DNS server remotely, enabling them to execute arbitrary commands, deploy malware, or disrupt services. Given that DNS servers play a crucial role in network infrastructure, a successful attack could lead to widespread network compromise, data breaches, and operational downtime.
Background and Context
Background on the vulnerability
CVE-2020-1350 was discovered in 2020 and affects the DNS server implementation in Windows Server. The vulnerability arises from improper handling of DNS query responses, particularly in the parsing of SIG (Signature) records. An attacker can send a specially crafted DNS query to the server, which triggers a buffer overflow, leading to remote code execution. The vulnerability is particularly severe because it can be exploited remotely without authentication, making it an attractive target for attackers.
Description of the Vulnerability (CVE-2020-1350)
The vulnerability occurs because the Windows DNS server fails to properly validate the length of certain DNS query responses, specifically SIG records. This leads to a buffer overflow condition, where data is written beyond the bounds of allocated memory. An attacker can exploit this flaw by sending a malicious DNS query that triggers the overflow, allowing them to execute arbitrary code on the server with SYSTEM privileges.
Root Cause Analysis
The root cause of CVE-2020-1350 is the improper validation and handling of SIG records in DNS query responses by the Windows DNS server. The server does not adequately check the length of these records, leading to a buffer overflow when processing them. This issue is particularly concerning in environments where the DNS server is exposed to untrusted networks or the internet.
Impact and Exploitation
The impact of CVE-2020-1350
Exploiting CVE-2020-1350 can have several severe impacts:
- Remote Code Execution: The most critical impact is the ability for an attacker to execute arbitrary commands on the server with SYSTEM privileges, potentially leading to full control over the DNS server.
- Network Compromise: An attacker could use this vulnerability to manipulate DNS responses, redirect traffic, or intercept communications, leading to a broader network compromise.
- Service Disruption: By executing arbitrary code, the attacker could disrupt DNS services, deploy ransomware or other malware, or delete critical data, leading to significant operational downtime.
Exploit
To exploit CVE-2020-1350, an attacker needs to send a specially crafted DNS query to the vulnerable Windows DNS server. The exploitation process involves:
- Identifying a target Windows Server running a vulnerable version of the DNS service.
- Crafting a DNS query that includes a malicious SIG record designed to exploit the buffer overflow.
- Sending the crafted query to the DNS server, where it is processed, and the buffer overflow triggers the execution of arbitrary code with SYSTEM privileges.
Proof of Concept (POC)
A basic Proof of Concept (POC) for CVE-2020-1350 might involve sending a DNS query with a specially crafted SIG record that triggers the buffer overflow. Example:
python code
import socket# Crafting a malicious DNS querymalicious_query = b'\x12\x34\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00\x07\x65\x78\x61\x6d\x70\x6c\x65\x03\x63\x6f\x6d\x00\x00\x10\x00\x03'# Sending the query to the target DNS serversock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)sock.sendto(malicious_query, ("<DNS-Server-IP>", 53))sock.close()This POC attempts to send a DNS query with a malformed SIG record that causes a buffer overflow on the target DNS server, demonstrating the vulnerability.
Note: This POC is for educational purposes only. Exploiting vulnerabilities without authorization is illegal and unethical.
Real-world Impact and Response
Timeline/changelog
- July 2020: Discovery of CVE-2020-1350 during a security review of Windows DNS servers.
- July 2020: Public disclosure of the vulnerability and release of patches by Microsoft to address the issue.
- August 2020: Security advisories and guidance issued to organizations to update their DNS servers and secure their networks against potential exploitation.
- September 2020: Continued monitoring for potential exploitation and providing additional updates as needed.
Observed Activity
Since its disclosure, CVE-2020-1350 has been actively targeted by attackers, particularly in environments where Windows DNS servers are exposed to untrusted networks. Exploitation has led to the compromise of DNS services, the deployment of malware, and significant operational disruptions.
Mass Scanning
Following the disclosure of CVE-2020-1350, there has been a significant increase in scanning activity targeting Windows DNS servers, particularly looking for systems running vulnerable versions. Attackers use automated tools to identify and exploit vulnerable servers.
Vulnerable Server Discovery
Vulnerable DNS servers can be discovered by attackers through targeted scanning or by analyzing network traffic for signs of outdated versions. Ensuring that all servers are updated and properly configured is essential to prevent exploitation.
Reasoning and Scoring
Corporate networks impacted globally
CVE-2020-1350 has the potential to impact corporate networks globally, particularly in environments where Windows DNS servers are used for critical network management and services. The vulnerability can be exploited to gain unauthorized access, execute arbitrary commands, and compromise the integrity of network infrastructure.
Corporate numbers impacted by countries
- United States: Extensive use of Windows DNS servers in enterprise and government environments, with many organizations potentially at risk.
- Europe: Significant adoption of Windows Server in finance, telecommunications, and critical infrastructure sectors, leading to potential exposure.
- Asia: Widespread use of Windows DNS servers in industries where secure network management is critical.
Additional Resources
For further reading and resources on CVE-2020-1350, consider the following:
- Microsoft Security Advisory
- NIST National Vulnerability Database
- OWASP Buffer Overflow Prevention Cheat Sheet
Acknowledgments
This article benefited from insights provided by Microsoft’s security team and contributions from the broader cybersecurity community, who shared valuable information regarding CVE-2020-1350.
Conclusion
Who should be paying attention to this?
System administrators, cybersecurity professionals, and organizations that use Windows Server for DNS management should prioritize attention to CVE-2020-1350. Ensuring that servers are updated and secure is critical for maintaining the integrity and confidentiality of network infrastructure.
Who is exploiting it and how?
CVE-2020-1350 has been actively exploited by attackers who identify vulnerable Windows DNS servers. These attackers craft malicious DNS queries designed to exploit the buffer overflow vulnerability, leading to remote code execution and full control over the server.
How are things likely to develop?
As more organizations apply updates and secure their DNS servers, the risk of widespread exploitation decreases. However, systems that remain unpatched are still vulnerable to attack, and the potential for targeted exploitation remains a concern. Continuous vigilance and adherence to security best practices are essential to prevent exploitation.
How long has it been around?
CVE-2020-1350 was discovered and disclosed in mid-2020, but the underlying issue with improper input validation may have existed in Windows DNS servers for some time before its discovery. This highlights the importance of regular security reviews and updates to address potential vulnerabilities in critical network infrastructure.
