Summary
AdonisJS Path Traversal in Multipart File Handling
Description
A Path Traversal (CWE-22) vulnerability in AdonisJS multipart file handling may allow a remote attacker to write arbitrary files to arbitrary locations on the server filesystem. This impacts @adonisjs/bodyparser through version 10.1.1 and 11.x prerelease versions prior to 11.0.0-next.6. This issue has been patched in @adonisjs/bodyparser versions 10.1.2 and 11.0.0-next.6.
Details
AdonisJS parses multipart/form-data via BodyParser and exposes uploads as MultipartFile. The issue is in the MultipartFile.move(location, options) default options. If options.name isn't provided, it defaults to the unsanitized client filename and builds the destination with path.join(location, name), allowing a traversal to escape the default or intended directory chosen by the developer. If options.overwrite isn't provided, it defaults to true, allowing file overwrites. The documentation previously demonstrated examples leading developers to this vulnerable code path.
Impact
Exploitation requires a reachable upload endpoint. If a developer uses MultipartFile.move() without the second options argument or without explicitly sanitizing the filename, an attacker can supply a crafted filename value containing traversal sequences, writing to a destination path outside the intended upload directory. This can lead to arbitrary file write on the server.
If the attacker can overwrite application code, startup scripts, or configuration files that are later executed/loaded, RCE is possible. RCE is not guaranteed and depends on filesystem permissions, deployment layout, and application/runtime behavior.
Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Fixes targeting v6 and v7 have been published below.
Frequently Asked Questions
- What is CVE-2026-21440? CVE-2026-21440 is a critical-severity path traversal vulnerability in @adonisjs/bodyparser (npm), affecting versions < 10.1.2. It is fixed in 10.1.2, 11.0.0-next.6. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
- Which versions of @adonisjs/bodyparser are affected by CVE-2026-21440? @adonisjs/bodyparser (npm) versions < 10.1.2 is affected.
- Is there a fix for CVE-2026-21440? Yes. CVE-2026-21440 is fixed in 10.1.2, 11.0.0-next.6. Upgrade to this version or later.
- Is CVE-2026-21440 exploitable, and should I be worried? Whether CVE-2026-21440 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-21440 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-21440?
- Upgrade
@adonisjs/bodyparserto 10.1.2 or later - Upgrade
@adonisjs/bodyparserto 11.0.0-next.6 or later
- Upgrade