---
id: "CVE-2026-114216"
kind: "vulnerability"
aliases: ["CVE-2026-114216"]
title: "Bandit: chunk extension parsing lets attackers smuggle requests past proxies"
severity: "medium"
cvss: 6.3
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", "no-front-end-proxy"]
published_at: "2026-10-26T14:16:29+00:00"
first_seen_at: "2026-10-26T14:30:36+00:00"
updated_at: "2026-10-26T14:32:38+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-114216", "first_seen_at": "2026-10-26T14:30:36+00:00"}]
---

# Bandit: chunk extension parsing lets attackers smuggle requests past proxies

Bandit, an Elixir HTTP server, accepts bare line feeds inside HTTP/1.1 chunked-encoding size lines and ignores the rest of the line. A front-end proxy that splits the line at a bare LF reads a different request boundary, so an unauthenticated attacker can smuggle a second request such as GET /admin past it.

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

## How to check

- Run `mix deps | grep bandit` or check `mix.lock` for the `bandit` version
- Confirm whether a reverse proxy or load balancer sits in front of Bandit, since the sources say deployments without one are not affected

## Fix

- Upgrade `bandit` to `1.14.0` or later, per the sources the affected range is from `1.12.4` before `1.14.0`

## Timeline

- 2026-10-26T14:30:36+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-114216

## From the sources

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in the HTTP/1.1 chunked body reader of mtrudel bandit allows an unauthenticated remote attacker to smuggle a second request past a front-end proxy via a chunk extension that contains a bare LF.

The chunked reader in lib/bandit/http1/socket.ex takes the chunk-size line to be everything up to the first CRLF and discards everything after ; without checking it against the RFC 9112 chunk-ext grammar, so bare LF, bare CR and other control bytes pass. A proxy that ends the size line at a bare LF reads 2;\nxx\r\n40\r\n... as one request whose second chunk holds a GET /admin, while Bandit ends the body early and dispatches GET /admin as a separate pipelined request. Deployments without such a proxy in front of Bandit are not affected.

This issue affects bandit: from 1.12.4 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_