CVE-2026-56814
Vulnérabilité moyenne dans plug (elixir-plug)
Description
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-rc.0 before 1.16.6, from 1.17.0 before 1.17.4, from 1.18.0 before 1.18.5, from 1.19.1 before 1.19.5, and from 1.20.0 before 1.20.3.
Gravité et risque d'exploitation
CVE-2026-56814 obtient un score CVSS de 6.9/10, soit une gravité moyenne. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 1.08 %, ce qui la place devant 64.6 % des CVE référencées.
Que faire ?
- Vérifiez si plug (versions <*, 1.17.0, c52b2f32c90bccd718202bafccb5f95594e30183, <1.18.5, 1.20.0, <1.20.3, <1.19.5, <1.17.4, 1.19.1, 1.4.0-rc.0, <1.16.6, 1.18.0) est présent sur votre parc.
- Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
- À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
- Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.
Références
- https://github.com/elixir-plug/plug/security/advisories/GHSA-95qv-c9g9-rm63
- https://cna.erlef.org/cves/CVE-2026-56814.html
- https://osv.dev/vulnerability/EEF-CVE-2026-56814
- https://github.com/elixir-plug/plug/commit/c52b2f32c90bccd718202bafccb5f95594e30183
- https://github.com/elixir-plug/plug/commit/981597d3a4271ede64373c7a731702a42c500dd6
- https://github.com/elixir-plug/plug/commit/56edca2ce35fe5589cd581644d8a4493fa5f484e
- https://github.com/elixir-plug/plug/commit/0ee8afcc61466dc5f7a8f048d0632c899165b81f
- https://github.com/elixir-plug/plug/commit/cae36053350e5215a4e0ca33cd130af9c5fc6364
- https://github.com/elixir-plug/plug/commit/f7effaed811c00b5f5bf817936bfd9c5df27b7dc
- https://github.com/elixir-plug/plug/commit/df97d3f17f808a9916a7700a701fb85314559d56
