Bandit: Unauthenticated one-shot DoS via `Transfer-Encoding: chunked` — CVE-2026-39803

Summary

### Summary Bandit's HTTP/1 chunked-body reader silently drops the request size cap that the application configures (e.g. `Plug.Parsers`' default 8 MB `length:`) and buffers the entire body in memory before the application sees it. An unauthenticated attacker can crash any Bandit-fronted Phoenix/Plug app (BEAM OOM) with a single `Transfer-Encoding: chunked` request to any URL. ### Details In…

Product

erlang: bandit

What to do

General, cautious steps (verify details in the official source):

• Prioritize patching or mitigation immediately (treat as actively risky).
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

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