---
id: "CVE-2026-115274"
kind: "vulnerability"
aliases: ["CVE-2026-115274"]
title: "Elixir: unbounded JSON integer parsing lets a request exhaust CPU and memory"
severity: "medium"
cvss: 6.9
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["elixir", "phoenix", "plug", "runtime", "self-hosted"]
not_affected_if: ["static-export", "trusted-input-only"]
published_at: "2026-10-30T09:17:14+00:00"
first_seen_at: "2026-10-30T09:29:38+00:00"
updated_at: "2026-10-30T09:30:36+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-115274", "first_seen_at": "2026-10-30T09:29:38+00:00"}]
---

# Elixir: unbounded JSON integer parsing lets a request exhaust CPU and memory

The Elixir standard library's JSON module converts integer literals of any length without a bound, so a single large JSON body can hold a scheduler for about a second. An unauthenticated attacker can cause denial of service by sending such a document to an exposed endpoint.

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

## How to check

- Run `elixir --version` and compare the Elixir version with the affected ranges.
- Look for `JSON.decode` or `JSON.decode!` calls, and for Phoenix apps generated by `phx.new` that parse request bodies with JSON in Plug.Parsers.

## Fix

- Elixir `1.18.6` or later for the 1.18 line
- Elixir `1.19.7` or later for the 1.19 line
- Elixir `1.20.5` or later for the 1.20 line

## Timeline

- 2026-10-30T09:29:38+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-115274

## From the sources

Improper Validation of Specified Quantity in Input vulnerability in the Elixir standard library's JSON module allows an unauthenticated attacker who supplies a JSON document to cause a denial of service through CPU and memory exhaustion.

JSON.decode/1 and JSON.decode!/1 convert each integer literal with erlang:binary_to_integer/1 and do not bound its length. A literal of one million digits decodes successfully but costs 100 to 300 times as much CPU as a string of the same length, so one request body of a few megabytes holds a scheduler for about a second. A literal of more than about 1.29 million digits raises SystemLimitError. Applications generated by phx.new decode request bodies with JSON in Plug.Parsers, before routing and authentication.

This issue affects elixir: from 1.18.0-rc.0 before 1.18.6, from 1.19.0-rc.0 before 1.19.7, and from 1.20.0-rc.0 before 1.20.5.

---

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