CVE-2026-21440 is a low severity vulnerability with a CVSS score of 0.0. Exploits are available; patches have been released and should be applied urgently.
Very low probability of exploitation
EPSS predicts the probability of exploitation in the next 30 days based on real-world threat data, complementing CVSS severity scores with actual risk assessment.
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.
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.
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.
Fixes targeting v6 and v7 have been published below.
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