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CVE-2021-21293 : Security Advisory and Response

Blaze servers running below version 0.14.15, including http4s-blaze-server users, are at risk due to unbounded connection acceptance vulnerability. Learn about the impact, technical details, and mitigation strategies.

Blaze, a Scala library used for building asynchronous pipelines, is affected by a vulnerability that allows unbounded connection acceptance, leading to file handle exhaustion. This vulnerability impacts servers running blaze-core before version 0.14.15 and users of http4s-blaze-server. The issue has a CVSS v3.1 base score of 7.5, indicating a high severity threat.

Understanding CVE-2021-21293

This section delves into the details of the vulnerability, its impact, and mitigation strategies.

What is CVE-2021-21293?

Blaze servers accepting connections unconditionally can lead to file handle exhaustion due to unbounded connection acceptance. This can significantly impact services under high request load.

The Impact of CVE-2021-21293

The vulnerability's high severity affects the availability of services due to file handle exhaustion, potentially causing service degradation and unresponsiveness.

Technical Details of CVE-2021-21293

Here are the technical aspects of the CVE, including vulnerability description, affected systems, and exploitation mechanism.

Vulnerability Description

Blaze's unbounded connection acceptance results in file handle exhaustion, impacting servers running blaze-core below version 0.14.15.

Affected Systems and Versions

Servers running blaze-core with versions below 0.14.15 and users of http4s-blaze-server <= 0.21.16 are vulnerable to this issue.

Exploitation Mechanism

The vulnerability occurs when connections are unconditionally accepted, draining OS resources and potentially causing service degradation.

Mitigation and Prevention

Learn how to address the CVE through immediate steps and long-term security practices.

Immediate Steps to Take

Users should update to blaze-core version 0.14.15 or above and implement the recommended workaround strategies listed in the GitHub Advisory.

Long-Term Security Practices

Implement regular security updates, monitor network connections, and follow best practices for securing network I/O pipelines.

Patching and Updates

Ensure timely patching of affected software versions and stay informed about security advisories from the relevant vendors.

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