---
id: CVE-2026-115274
title: >-
  Unbounded integer parsing in JSON.decode/1 enables CPU and memory exhaustion
  denial of service in Elixir
summary: >-
  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.…
severity: medium
cvss: 6.9
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N'
cvssSource: cna
cwe:
  - CWE-1284
vendor: elixir-lang
product: elixir
affected:
  - elixir >= 1.18.0-rc.0 < 1.18.6
  - elixir >= 1.19.0-rc.0 < 1.19.7
  - elixir >= 1.20.0-rc.0 < 1.20.5
  - elixir-lang/elixir >= 793c1147210388587defb649f25f293ffbfa6b1b < *
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-30T16:51:17.679403Z'
exploitAvailable: true
published: '2026-10-30'
updated: '2026-10-30'
sourceUpdated: '2026-10-30T16:51:45.396Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-115274'
references:
  - url: >-
      https://github.com/elixir-lang/elixir/security/advisories/GHSA-rp5q-xqhq-926h
    label: >-
      Unbounded integer parsing in JSON.decode/1 enables CPU and memory
      exhaustion denial of service in Elixir
  - url: 'https://cna.erlef.org/cves/CVE-2026-115274.html'
    label: EEF CNA record for CVE-2026-115274
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-115274'
    label: OSV record EEF-CVE-2026-115274
  - url: >-
      https://github.com/elixir-lang/elixir/commit/793c1147210388587defb649f25f293ffbfa6b1b
    label: Introducing commit 793c114 in elixir-lang/elixir
  - url: >-
      https://github.com/elixir-lang/elixir/commit/c81f12265919c34a0d5134f1905a4eb4edaea1c2
    label: Fix commit c81f122 in elixir-lang/elixir
  - url: >-
      https://github.com/elixir-lang/elixir/commit/7154e8781da9fd016a973ea01776a011c8b5726a
    label: Fix commit 7154e87 in elixir-lang/elixir
  - url: >-
      https://github.com/elixir-lang/elixir/commit/cd158efacdc10b30232864251747dff9b8387dfe
    label: Fix commit cd158ef in elixir-lang/elixir
  - url: >-
      https://github.com/elixir-lang/elixir/commit/ee5cc23f8928aa5a0f25bb7f28e42ecfc7b7d396
    label: Fix commit ee5cc23 in elixir-lang/elixir
tags:
  - cve.org
  - exploit-available
epss: 0.00498
epssPercentile: 0.42957
ingestedAt: '2026-11-05T16:24:31.097Z'
---

## Overview

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.

## Affected

- `elixir >= 1.18.0-rc.0 < 1.18.6`
- `elixir >= 1.19.0-rc.0 < 1.19.7`
- `elixir >= 1.20.0-rc.0 < 1.20.5`
- `elixir-lang/elixir >= 793c1147210388587defb649f25f293ffbfa6b1b < *`

## Remediation

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

### Workarounds

Decode untrusted JSON with an integer decoder that rejects long digit runs before conversion:

defmodule SafeJSON do
  def decode!(binary) do
    case JSON.decode(binary, :ok, integer: &safe_integer/1) do
      {decoded, :ok, ""} -> decoded
      _ -> raise ArgumentError, "invalid JSON"
    end
  end

  defp safe_integer(digits) when byte_size(digits) <= 1024, do: String.to_integer(digits)
  defp safe_integer(_digits), do: raise(ArgumentError, "integer too long")
end

In Phoenix, pass SafeJSON to Plug.Parsers as json_decoder instead of Phoenix.json_library().