---
id: "CVE-2026-111101"
kind: "vulnerability"
aliases: ["CVE-2026-111101"]
title: "Bandit: unlimited tiny HTTP chunks let one request exhaust server memory"
severity: "high"
cvss: 8.7
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["bandit", "elixir", "package", "phoenix", "self-hosted"]
not_affected_if: ["bandit-1.14.0-or-later"]
published_at: "2026-10-26T14:16:27+00:00"
first_seen_at: "2026-10-26T14:30:36+00:00"
updated_at: "2026-10-26T14:32:11+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-111101", "first_seen_at": "2026-10-26T14:30:36+00:00"}]
---

# Bandit: unlimited tiny HTTP chunks let one request exhaust server memory

Bandit, an Elixir HTTP server, has no limit on the number of chunks in a chunked request body, so each 1-byte chunk adds memory and CPU cost. An unauthenticated remote attacker can send a body of many tiny chunks and exhaust server memory and CPU, even if the route never reads the body.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the bandit version in `mix.lock` or with `mix deps | grep bandit`
- Look for `{:bandit,` in `mix.exs` to confirm the dependency is present

## Fix

- Upgrade bandit to `1.14.0` or later in `mix.exs`, then run `mix deps.update bandit`

## Timeline

- 2026-10-26T14:30:36+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-111101

## From the sources

Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/1.1 chunked body reader of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory and CPU via a request body made of many 1-byte chunks.

The chunked reader in lib/bandit/http1/socket.ex keeps every chunk as its own list cell and binary term until IO.iodata_to_binary/1 joins them, and nothing limits the number of chunks. The :length option of read_body/2 counts only data bytes, so tiny chunks cost far more memory than their payload: 48 MB of 1-byte chunks grew one handler process to about 500 MB and took about 6 s of CPU. The route does not need to read the body, because on keep-alive connections ensure_completed/1 drains unread bodies through the same reader.

This issue affects bandit: from 0.1.0 before 1.14.0.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_