---
id: CVE-2026-110499
title: >-
  Client-chosen HPACK encoder table size is applied uncapped, growing
  per-connection state with every response in Bandit
summary: >-
  Allocation of Resources Without Limits or Throttling vulnerability in the
  HTTP/2 implementation of mtrudel bandit allows an unauthenticated remote
  attacker to grow per-connection memory and CPU cost without bound via a large
  SETTINGS_HEA…
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 >= 0.3.6 < 1.14.0
  - >-
    mtrudel/bandit >= 0e68313fab9d204257ebad5c447e4cd9cea8e0ea <
    220b9dfd27f9a21305be2afc75cbe585ddc24e7a
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-26T15:02:00.207666Z'
published: '2026-10-26'
updated: '2026-10-26'
sourceUpdated: '2026-10-26T15:35:50.929Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-110499'
references:
  - url: 'https://github.com/mtrudel/bandit/security/advisories/GHSA-47x4-3fxf-82fr'
    label: >-
      Client-chosen HPACK encoder table size is applied uncapped, growing
      per-connection state with every response in Bandit
  - url: 'https://cna.erlef.org/cves/CVE-2026-110499.html'
    label: EEF CNA record for CVE-2026-110499
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-110499'
    label: OSV record EEF-CVE-2026-110499
  - url: >-
      https://github.com/mtrudel/bandit/commit/0e68313fab9d204257ebad5c447e4cd9cea8e0ea
    label: Introducing commit 0e68313 in mtrudel/bandit
  - url: >-
      https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a
    label: Fix commit 220b9df in mtrudel/bandit
tags:
  - cve.org
ingestedAt: '2026-10-26T14:27:31.820Z'
---

## Overview

Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/2 implementation of mtrudel bandit allows an unauthenticated remote attacker to grow per-connection memory and CPU cost without bound via a large SETTINGS_HEADER_TABLE_SIZE. Bandit resizes its HPACK encoder table to whatever size the client advertises, up to 2^32-1 bytes, and indexes response headers into it. Because responses carry distinct values such as date or content-length, nothing is evicted and the table grows with every response for the life of the connection, while each lookup scans it linearly.

The SETTINGS handling in Bandit.HTTP2.Connection (lib/bandit/http2/connection.ex) passes remote_settings.header_table_size to HPAX.resize/2 with no server-side cap, and encode_headers encodes every response header as :store. Serving N responses on one connection therefore costs O(N²) CPU in the connection process.

This issue affects bandit: from 0.3.6 before 1.14.0.

## Affected

- `bandit >= 0.3.6 < 1.14.0`
- `mtrudel/bandit >= 0e68313fab9d204257ebad5c447e4cd9cea8e0ea < 220b9dfd27f9a21305be2afc75cbe585ddc24e7a`

## Remediation

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

### Workarounds

From 0.7.0, cap the requests one HTTP/2 connection may serve, for example with http_2_options: [max_requests: 1000], so each connection and its encoder table is closed before the cost grows large. Alternatively, disable HTTP/2 with http_2_options: [enabled: false].