GHSA-g77h-45rf-hcx4 ExifReader HEIC/AVIF ISO-BMFF parser throws uncaught RangeError on truncated boxes

• npm exifreader: < 4.40.1 → fixed in 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 >> 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: ```text heic/free: RangeError: Offset is outside the bounds of the DataView RangeError: Offset is outside the bounds of the DataView at DataView.prototype.getUint8 () 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: ```js 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 issue for services that parse user-provided HEIC/AVIF files with ExifReader. A minimal attacker-controlled image buffer can cause an unhandled exception in the parser and abort the surrounding request/worker if the embedding application does not catch every parse error. Suggested severity: Medium. Suggested CVSS: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`. Suggested fix Add explicit bounds checks before every `DataView` read in the ISO-BMFF box parser, especially: • before reading the 64-bit extended size fields in `getBoxLength()`; • before reading the full-box version byte in `parseBox()`; • before descending into `parseSubBoxes()` when a declared box length exceeds available bytes; • ensure `findMetaBox()` breaks on boxes whose declared length is invalid or not fully present. A regression test should cover `ftyp/heic` and `ftyp/avif` followed by an 8-byte empty `free`/unknown box and by a truncated extended-size box.