elixir-plug up to 1.20.2 Multipart Request-Body Parser multipart.ex parse_multipart/2 filename denial of service

Summaryinfo

A vulnerability was found in elixir-plug plug up to 1.16.5/1.17.3/1.18.4/1.19.4/1.20.2. It has been declared as problematic. This impacts the function parse_multipart/2 of the file lib/plug/parsers/multipart.ex of the component Multipart Request-Body Parser. Such manipulation of the argument filename leads to denial of service. This vulnerability is traded as CVE-2026-56814. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in elixir-plug plug up to 1.16.5/1.17.3/1.18.4/1.19.4/1.20.2 and classified as problematic. Affected by this issue is the function parse_multipart/2 of the file lib/plug/parsers/multipart.ex of the component Multipart Request-Body Parser. The manipulation of the argument filename with an unknown input leads to a denial of service vulnerability. Using CWE to declare the problem leads to CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. Impacted is availability. CVE summarizes:

Plug.Parsers.MULTIPART, the multipart request-body parser used to handle file uploads and multipart forms, does not enforce its :length budget against all consumed resources, allowing an unauthenticated remote attacker to cause denial of service. The parser charges the :length limit only for part body bytes; part header bytes are never counted, and a part with an empty body costs zero. Because every part whose Content-Disposition carries a non-empty filename creates a fresh temporary file (via Plug.Upload) and retains a Plug.Upload struct for the duration of the request, an attacker can send a single request composed of many empty-body file parts. Such a request stays well under the configured :length limit (8,000,000 bytes by default) while creating one temporary file per part, leading to inode and disk exhaustion and unbounded memory growth. Any application using Plug.Parsers with the :multipart parser is affected, and no authentication is required, only reachability of a multipart endpoint over HTTP. This vulnerability is associated with program files lib/plug/parsers/multipart.ex and program routines Plug.Parsers.MULTIPART.parse_multipart/2, Plug.Parsers.MULTIPART.parse_multipart_headers/5, Plug.Parsers.MULTIPART.parse_multipart_body/4, and Plug.Parsers.MULTIPART.parse_multipart_file/4. This issue affects plug: from 1.4.0 before 1.16.6, from 1.17.0 before 1.17.4, from 1.18.0 before 1.18.5, from 1.19.0 before 1.19.5, and from 1.20.0 before 1.20.3.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-56814 since 06/23/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

Upgrading to version 1.16.6, 1.17.4, 1.18.5, 1.19.5 or 1.20.3 eliminates this vulnerability.

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Productinfo

Vendor

• elixir-plug

Name

• plug

Version

• 1.16.0
• 1.16.1
• 1.16.2
• 1.16.3
• 1.16.4
• 1.16.5
• 1.17.0
• 1.17.1
• 1.17.2
• 1.17.3
• 1.18.0
• 1.18.1
• 1.18.2
• 1.18.3
• 1.18.4
• 1.19.0
• 1.19.1
• 1.19.2
• 1.19.3
• 1.19.4
• 1.20.0
• 1.20.1
• 1.20.2

Website

• Product: https://github.com/elixir-plug/plug/

CPE 2.3info

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CPE 2.2info

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