fastify busboy up to 3.2.1 Multipart Part-Header Parser neutralization for logs

Summaryinfo

A vulnerability labeled as problematic has been found in fastify busboy up to 3.2.1. Affected by this issue is some unknown functionality of the component Multipart Part-Header Parser. Executing a manipulation can lead to neutralization for logs. The identification of this vulnerability is CVE-2026-74866. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in fastify busboy up to 3.2.1. It has been declared as problematic. This vulnerability affects an unknown part of the component Multipart Part-Header Parser. The manipulation with an unknown input leads to a neutralization for logs vulnerability. The CWE definition for the vulnerability is CWE-117. The product does not neutralize or incorrectly neutralizes output that is written to logs. As an impact it is known to affect integrity. CVE summarizes:

@fastify/busboy is a multipart form-data parser for Node.js. Its multipart part-header parser splits header lines only on the two-byte carriage-return line-feed sequence, so a lone carriage return or line feed embedded in a part header is not treated as a line break and is carried verbatim into the parsed Content-Disposition filename and field name handed to the application. An attacker who uploads a file whose filename or field name contains a bare carriage return or line feed can inject control characters into consumers that trust the parser to return clean values, enabling filesystem filename pollution, log forging, or header injection when the value is forwarded to a carriage-return-sensitive sink. All versions of @fastify/busboy up to and including 3.2.1 are affected. The issue is fixed in version 3.2.2, which rejects any header line that still contains a bare carriage return or line feed. Users should upgrade to 3.2.2, and consumers such as @fastify/multipart should bump their @fastify/busboy dependency to pull in the fix.

The advisory is available at github.com. This vulnerability was named CVE-2026-74866 since 08/17/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. The technical details are unknown and an exploit is not available.

Upgrading to version 3.2.2 eliminates this vulnerability.

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Productinfo

Vendor

• fastify

Name

• busboy

Version

• 3.2.0
• 3.2.1

Website

• Product: https://github.com/fastify/busboy/

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