---
id: "CVE-2026-97200"
kind: "vulnerability"
aliases: ["CVE-2026-97200"]
title: "hackney: malicious server can exhaust client memory with large responses"
severity: "high"
cvss: 8.2
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["elixir", "erlang", "hackney", "package"]
not_affected_if: ["hackney-4.9.0-or-later", "hackney-not-used", "trusted-servers-only"]
published_at: "2026-10-26T14:16:42+00:00"
first_seen_at: "2026-10-26T14:30:37+00:00"
updated_at: "2026-10-26T14:32:17+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-97200", "first_seen_at": "2026-10-26T14:30:37+00:00"}]
---

# hackney: malicious server can exhaust client memory with large responses

The Erlang HTTP client hackney buffers entire response bodies without any size limit, and decompresses them in one step. A malicious HTTP server the client calls can send an oversized or highly compressed body and exhaust the client's memory.

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

## How to check

- Check the hackney version in `rebar.lock` or `mix.lock` (or the lock file for your build tool) and see whether it falls in `2.0.0-beta.1` to before `4.9.0`.
- Look for calls to `hackney:request/5` or `hackney:body/1` that fetch from servers you do not control.

## Fix

- Upgrade hackney to `4.9.0` or later.

## Timeline

- 2026-10-26T14:30:37+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-97200

## From the sources

Allocation of Resources Without Limits or Throttling vulnerability in hackney_conn in benoitc hackney allows a malicious HTTP server to exhaust client memory via an oversized or highly compressed response body. hackney:request/5 and hackney:body/1 return the whole response body, and nothing bounds how much the connection process buffers. Any server the client requests can trigger it.

hackney_conn:read_full_body/2 and the HTTP/2 and HTTP/3 accumulators append every chunk until the body ends. With {auto_decompress, true} the buffered body is then inflated in one step with zlib:gunzip/1 or zlib:inflate/2, which return the whole output at once.

This issue affects hackney: from 2.0.0-beta.1 before 4.9.0.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_