---
id: "CVE-2026-113436"
kind: "vulnerability"
aliases: ["CVE-2026-113436"]
title: "Bandit: header integer parsing lets remote requests consume server CPU"
severity: "high"
cvss: 8.7
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["bandit", "elixir", "http-server", "package", "phoenix", "self-hosted"]
not_affected_if: ["bandit-1.14.0-or-later", "not-using-bandit"]
published_at: "2026-10-26T14:16:28+00:00"
first_seen_at: "2026-10-26T14:30:36+00:00"
updated_at: "2026-10-26T14:32:08+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-113436", "first_seen_at": "2026-10-26T14:30:36+00:00"}]
---

# Bandit: header integer parsing lets remote requests consume server CPU

Bandit's header integer parser handles content-length and Host port values one digit at a time with no length limit, so very long digit strings cost quadratic CPU time. An unauthenticated remote attacker can send such headers, and over HTTP/2 reuse a stored value to keep the server busy with little traffic.

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

## How to check

- Check the bandit version in the project's lockfile (`mix.lock`) or run `mix deps | grep bandit`
- Confirm the lockfile resolves bandit below `1.14.0`

## Fix

- Upgrade bandit to `1.14.0` or later in `mix.exs` and run `mix deps.update bandit`
- Redeploy the application after the upgrade

## Timeline

- 2026-10-26T14:30:36+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-113436

## From the sources

Inefficient Algorithmic Complexity vulnerability in the header integer parser of mtrudel bandit allows an unauthenticated remote attacker to consume server CPU via a content-length value or a Host or :authority port made of thousands of digits.

Bandit.Headers.parse_integer/2 in lib/bandit/headers.ex builds the number one digit at a time with no limit on the digit count, allocating a new bignum at each step, so one value costs time quadratic in its length. It runs on raw request input over HTTP/1 and HTTP/2, before any range check. Over HTTP/2, a 4,000-digit value can be stored once in the HPACK dynamic table and re-sent on each new stream for about one byte: 124 KB of traffic kept the server busy for 27.9 s.

This issue affects bandit: from 1.0.0-pre.7 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_