---
id: CVE-2026-111101
title: >-
  HTTP/1.1 chunked request bodies made of 1-byte chunks amplify memory use in
  Bandit
summary: >-
  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 ch…
severity: high
cvss: 8.7
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'
cvssSource: cna
cwe:
  - CWE-770
vendor: mtrudel
product: bandit
affected:
  - bandit >= 0.1.0 < 1.14.0
  - >-
    mtrudel/bandit >= 7201270c34b90f6c9e15c0386c2bb802c0c72ab4 <
    220b9dfd27f9a21305be2afc75cbe585ddc24e7a
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-26T15:10:33.224480Z'
published: '2026-10-26'
updated: '2026-10-26'
sourceUpdated: '2026-10-26T15:35:51.401Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-111101'
references:
  - url: 'https://github.com/mtrudel/bandit/security/advisories/GHSA-jwh3-j29h-qfmw'
    label: >-
      HTTP/1.1 chunked request bodies made of 1-byte chunks amplify memory use
      in Bandit
  - url: 'https://cna.erlef.org/cves/CVE-2026-111101.html'
    label: EEF CNA record for CVE-2026-111101
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-111101'
    label: OSV record EEF-CVE-2026-111101
  - url: >-
      https://github.com/mtrudel/bandit/commit/7201270c34b90f6c9e15c0386c2bb802c0c72ab4
    label: Introducing commit 7201270 in mtrudel/bandit
  - url: >-
      https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a
    label: Fix commit 220b9df in mtrudel/bandit
tags:
  - cve.org
ingestedAt: '2026-10-26T14:27:31.818Z'
---

## Overview

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.

## Affected

- `bandit >= 0.1.0 < 1.14.0`
- `mtrudel/bandit >= 7201270c34b90f6c9e15c0386c2bb802c0c72ab4 < 220b9dfd27f9a21305be2afc75cbe585ddc24e7a`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

### Workarounds

From 0.7.0, a server whose clients and proxies all speak HTTP/2 can disable HTTP/1 with http_1_options: [enabled: false], so that the vulnerable chunked body reader never runs.