---
id: CVE-2026-111103
title: >-
  HTTP/2 StreamError recovery rolls back connection state and bypasses
  per-connection limits in Bandit
summary: >-
  Improper Cleanup on Thrown Exception vulnerability in the HTTP/2 handler of
  mtrudel bandit allows an unauthenticated remote attacker to bypass
  per-connection resource limits via a single TCP write that carries several
  frames, one of whic…
severity: high
cvss: 8.2
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'
cvssSource: cna
cwe:
  - CWE-460
vendor: mtrudel
product: bandit
affected:
  - bandit >= 1.9.0 < 1.14.0
  - >-
    mtrudel/bandit >= 3ad49c80c268891e7cc412e69649115456638e59 <
    220b9dfd27f9a21305be2afc75cbe585ddc24e7a
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-26T15:11:27.499001Z'
published: '2026-10-26'
updated: '2026-10-26'
sourceUpdated: '2026-10-26T15:35:51.229Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-111103'
references:
  - url: 'https://github.com/mtrudel/bandit/security/advisories/GHSA-2238-pgfc-w82m'
    label: >-
      HTTP/2 StreamError recovery rolls back connection state and bypasses
      per-connection limits in Bandit
  - url: 'https://cna.erlef.org/cves/CVE-2026-111103.html'
    label: EEF CNA record for CVE-2026-111103
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-111103'
    label: OSV record EEF-CVE-2026-111103
  - url: >-
      https://github.com/mtrudel/bandit/commit/3ad49c80c268891e7cc412e69649115456638e59
    label: Introducing commit 3ad49c8 in mtrudel/bandit
  - url: >-
      https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a
    label: Fix commit 220b9df in mtrudel/bandit
tags:
  - cve.org
ingestedAt: '2026-10-26T14:27:31.819Z'
---

## Overview

Improper Cleanup on Thrown Exception vulnerability in the HTTP/2 handler of mtrudel bandit allows an unauthenticated remote attacker to bypass per-connection resource limits via a single TCP write that carries several frames, one of which raises a stream error.

When a frame raises StreamError partway through a chunk, Bandit.HTTP2.Handler.handle_data/3 sends RST_STREAM and continues with the connection state from before the chunk, dropping the rest of it. Streams opened by earlier frames in the chunk keep running their Plug calls, but the stream counts, last_stream_id, the rapid-reset timestamps, the HPACK decoder state and the buffer roll back, so max_concurrent_streams, max_requests and the rapid-reset limiter never see those streams. A client that sends one HEADERS frame more than max_concurrent_streams in each write has the extra refused and the others forgotten: with a limit of 10, five such writes run 50 Plug calls at once.

This issue affects bandit: from 1.9.0 before 1.14.0.

## Affected

- `bandit >= 1.9.0 < 1.14.0`
- `mtrudel/bandit >= 3ad49c80c268891e7cc412e69649115456638e59 < 220b9dfd27f9a21305be2afc75cbe585ddc24e7a`

## Remediation

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

### Workarounds

Disable HTTP/2 with http_2_options: [enabled: false], so that the vulnerable HTTP/2 handler never runs.