CVE-2021-27293 : Security Advisory and Response

A vulnerability has been identified in RestSharp < 106.11.8-alpha.0.13 that could lead to Regular Expression Denial of Service (ReDoS) attacks. This CVE-2021-27293 allows a malicious server to trigger a Denial of Service by causing the client using RestSharp to process a malicious string indefinitely.

Understanding CVE-2021-27293

This section provides an insight into the nature of the vulnerability and its potential impact.

What is CVE-2021-27293?

The vulnerability in RestSharp < 106.11.8-alpha.0.13 arises from a regular expression that is susceptible to ReDoS attacks when converting strings to DateTimes. When processed by RestSharp, a malicious string can cause prolonged processing, enabling a remote server to launch a Denial of Service attack.

The Impact of CVE-2021-27293

The exploitation of this vulnerability allows threat actors to disrupt the availability of services by exploiting the ReDoS weakness in RestSharp. By responding with a crafted string, attackers can force affected clients into extended processing loops, ultimately leading to Denial of Service conditions.

Technical Details of CVE-2021-27293

Explore the technical aspects related to the CVE, including how systems and versions are affected and the mechanism of exploitation.

Vulnerability Description

RestSharp versions prior to 106.11.8-alpha.0.13 are impacted by a ReDoS vulnerability due to improper handling of regular expressions during string conversions. This flaw enables malicious servers to overload client processing by sending specially crafted strings, resulting in DoS conditions.

Affected Systems and Versions

All versions of RestSharp below 106.11.8-alpha.0.13 are impacted by this vulnerability. Users of affected versions are at risk of ReDoS attacks exploiting the DateTime string conversion functionality.

Exploitation Mechanism

The vulnerability in RestSharp allows threat actors to exploit the regular expression processing that converts strings into DateTimes. By sending a maliciously crafted string in server responses, attackers can trigger infinite processing loops on clients, leading to Denial of Service.

Mitigation and Prevention

Discover the immediate steps to secure systems, best security practices, and the importance of timely patching and updates.

Immediate Steps to Take

Users of RestSharp should update to version 106.11.8-alpha.0.13 or newer to mitigate the risk of ReDoS attacks. Additionally, it is advisable to implement input validation and restrict server responses to prevent malicious exploitation.

Long-Term Security Practices

To enhance cybersecurity posture, organizations should enforce secure coding practices, conduct regular security assessments, and raise awareness among developers and users regarding potential vulnerabilities in third-party libraries.

Patching and Updates

Regularly check for security updates from RestSharp and promptly apply patches. Stay informed about new vulnerabilities and their mitigations to reduce the risk of future exploitation.