---
id: "CVE-2026-108525"
kind: "vulnerability"
aliases: ["CVE-2026-108525"]
title: "Bandit: HTTP/2 flow-control gap lets remote clients exhaust server memory"
severity: "high"
cvss: 8.7
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["bandit", "elixir", "http2", "package", "phoenix", "self-hosted"]
not_affected_if: ["bandit-1.14.0-or-later", "no-http2-listener"]
published_at: "2026-10-26T14:16:24+00:00"
first_seen_at: "2026-10-26T14:30:36+00:00"
updated_at: "2026-10-26T14:32:17+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-108525", "first_seen_at": "2026-10-26T14:30:36+00:00"}]
---

# Bandit: HTTP/2 flow-control gap lets remote clients exhaust server memory

Bandit, an Elixir HTTP server, does not enforce the HTTP/2 receive window, so a client can send DATA frames past the window and have them queued in memory. An unauthenticated remote attacker can exhaust server memory and crash the BEAM node.

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

## How to check

- Check the Bandit version in `mix.lock` or `mix deps` output; affected versions are from `0.3.1` before `1.14.0`.
- Confirm HTTP/2 is served by Bandit, e.g. the endpoint is configured with `plug_cowboy` replaced by Bandit or `http: [protocol_options: [http_1: false]]` style settings the sources do not specify; unknown beyond the version check.

## Fix

- Upgrade Bandit to `1.14.0` or later.
- Redeploy the application and restart the BEAM node.

## Timeline

- 2026-10-26T14:30:36+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-108525

## From the sources

Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/2 implementation of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory via DATA frames sent past the advertised receive window. The attacker requests a response larger than the 65,535-byte initial window and withholds WINDOW_UPDATE, so the stream process blocks while sending and stops reading, then floods small DATA frames on that stream. Every frame is queued in the stream's mailbox until the BEAM node runs out of memory.

Bandit.HTTP2.Connection.handle_frame/3 in lib/bandit/http2/connection.ex forwards each DATA frame to the stream process without consulting the receive window, and Bandit.HTTP2.FlowControl.compute_recv_window/2 replenishes the window as data arrives rather than as it is consumed, and never answers a violation with FLOW_CONTROL_ERROR.

This issue affects bandit: from 0.3.1 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_