devalue Vulnerability: Quadratic Expansion in uneval

Executive Summary

A vulnerability in the devalue library, tracked as GHSA-mcm9-63f2-9j32, can cause quadratic expansion in the uneval function when handling repeated primitive strings. This issue, rated with a CVSS score of 8.2, affects devalue versions <= 5.9.2 and can lead to performance issues and potential amplification attacks. Users should update to version 5.9.3 or later.

Technical Analysis

The vulnerability is caused by the uneval function's inability to handle repeated primitive strings efficiently, leading to quadratic expansion. This occurs when data that was previously parsed is then passed to uneval, potentially turning a small payload into a very large serialized string. The root cause is related to the improper handling of highly compressed data, which aligns with CWE-409.

How It Gets Exploited

An attacker would need to craft a specific payload that, when parsed and then passed to uneval, could cause this quadratic expansion. The starting position for an attacker would likely involve being able to input data that gets parsed and then unevaluated, possibly through a web application or similar interface that uses the devalue library. The specific action would involve sending a crafted payload that includes repeated primitive strings. When this payload is parsed and then passed to uneval, the function fails to efficiently handle the repeated strings, leading to a large serialized string. The attacker gains the ability to cause performance issues or amplification attacks.

Impact Assessment

The impact of this vulnerability is significant, with a CVSS score of 8.2 indicating high severity. It affects users of the devalue library, specifically those on versions <= 5.9.2. An attacker could exploit this to cause denial-of-service (DoS) conditions or amplify data, leading to potential performance degradation or resource exhaustion.

Recommended Actions

- Update the devalue library to version 5.9.3 or later. - Implement input validation and sanitization for data that will be parsed and passed to uneval. - Monitor for unusual patterns of data amplification or performance degradation that could indicate exploitation attempts.

Sources

- GitHub Security Advisories: GHSA-mcm9-63f2-9j32