CVE-2018-7560 in aws-lambda-multipart-parser NPM Package
Summary
by MITRE
index.js in the Anton Myshenin aws-lambda-multipart-parser NPM package before 0.1.2 has a Regular Expression Denial of Service (ReDoS) issue via a crafted multipart/form-data boundary string.
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Analysis
by VulDB Data Team • 02/16/2023
The vulnerability identified as CVE-2018-7560 resides within the aws-lambda-multipart-parser npm package, specifically in the index.js file of versions prior to 01.2. This issue manifests as a Regular Expression Denial of Service (ReDoS) vulnerability that exploits a flaw in how the package processes multipart/form-data boundary strings. The vulnerability occurs when a maliciously crafted boundary string is submitted to the parser, causing the regular expression engine to enter into a catastrophic backtracking state that consumes excessive CPU resources and can lead to service unavailability.
The technical flaw stems from the implementation of regular expressions within the multipart parser that fail to properly validate or sanitize boundary string inputs. When the parser encounters a specially crafted boundary string, the regular expression pattern becomes vulnerable to exponential backtracking behavior, where the regex engine attempts to match the input against the pattern using an exponential number of operations. This creates a denial of service condition where legitimate requests cannot be processed due to the parser being overwhelmed by the malformed input. The vulnerability is categorized under CWE-400 as "Uncontrolled Resource Consumption" and specifically relates to CWE-1333 which addresses "Improper Regular Expression" issues.
The operational impact of this vulnerability extends beyond simple service disruption to potentially affect server availability and system performance within applications that rely on the aws-lambda-multipart-parser package. When exploited, the ReDoS condition can cause the lambda function to consume excessive processing time, leading to timeouts and resource exhaustion. This is particularly concerning in serverless environments where functions may be invoked frequently and resource constraints are tight. The vulnerability affects systems that process multipart form data submissions, commonly found in web applications, API endpoints, and serverless functions that handle file uploads or form submissions.
Mitigation strategies for CVE-2018-7560 involve immediate patching of the aws-lambda-multipart-parser package to version 0.1.2 or later where the regular expression vulnerabilities have been addressed. Organizations should implement input validation and sanitization measures to filter out potentially malicious boundary strings before they reach the parser. Additionally, rate limiting and resource monitoring should be implemented to detect and prevent exploitation attempts. The ATT&CK framework categorizes this vulnerability under T1499.004 "Endpoint Denial of Service" as it represents a method of causing service unavailability through resource exhaustion. System administrators should also consider implementing security scanning tools that can detect vulnerable npm packages and ensure that all dependencies are regularly updated to address known security issues. The remediation process should include thorough testing of the patched version to ensure that legitimate multipart form data processing continues to function correctly while the vulnerability is eliminated.