CVE-2021-26843 : Security Advisory and Response
Learn about CVE-2021-26843, a Denial-of-Service flaw in sthttpd through version 2.27.1 that allows a daemon crash via crafted HTTP GET requests. Explore impact, technical details, and mitigation.
An issue was discovered in sthttpd through version 2.27.1 where the de_dotdot function may cause a Denial-of-Service (daemon crash) on systems with the strcpy function implemented with memcpy. This vulnerability can be exploited by sending a crafted filename via an HTTP GET request. It is similar to CVE-2017-10671 but occurs in a different part of the de_dotdot function.
Understanding CVE-2021-26843
This section provides insights into the impact, technical details, mitigation, and prevention methods related to CVE-2021-26843.
What is CVE-2021-26843?
CVE-2021-26843 is a vulnerability in sthttpd through version 2.27.1 that can lead to a Denial-of-Service (DoS) situation due to overlapping memory ranges passed to memcpy.
The Impact of CVE-2021-26843
The vulnerability allows attackers to trigger a daemon crash via an HTTP GET request containing a specially crafted filename, posing a risk of service disruption.
Technical Details of CVE-2021-26843
This section delves into the specifics of the vulnerability, affected systems, versions, and how the exploitation can occur.
Vulnerability Description
The issue arises from the de_dotdot function in sthttpd, affecting systems using strcpy implemented with memcpy, leading to a DoS condition.
Affected Systems and Versions
All systems using sthttpd up to version 2.27.1 are affected by this vulnerability when strcpy is implemented with memcpy.
Exploitation Mechanism
Exploitation can be achieved by crafting a filename in an HTTP GET request to trigger the de_dotdot function, causing overlapping memory ranges and eventually leading to a daemon crash.
Mitigation and Prevention
Discover the necessary steps to safeguard your systems from CVE-2021-26843 and prevent potential exploitation.
Immediate Steps to Take
Apply patches provided by the vendor or mitigate the risk by implementing relevant security measures and controls.
Long-Term Security Practices
Ensure secure coding practices are followed, monitor for anomalous HTTP requests, and conduct regular security assessments to identify and address vulnerabilities.
Patching and Updates
Stay informed about security updates from the sthttpd project and promptly apply patches to eliminate the vulnerability.