Dompdf is an HTML to PDF converter for PHP. Versions 3.15 and prior accept a BMP image and generates a PDF-compatible PNG based only on its declared header dimensions and never bounds width × height before the image is converted through GD. A 58-byte BMP whose header declares e.g. 6000×6000 is accepted and later drives imagecreatetruecolor($width, $height) (and PHP's native BMP decoder) to allocate the full pixel canvas. A payload can fit in a single HTTP request: the BMP can be inlined as a data:image/bmp;base64,… URI inside attacker-controlled HTML, so no upload, no remote fetch, and no chroot-reachable file is required. I measured a 169-byte request driving a dompdf render to ~412 MB peak RSS and ~4.8 s of CPU/wall time, versus ~34 MB for an identically-sized benign request — roughly a 12× memory amplification per request, repeatable and unauthenticated. This issue has been fixed in version 3.16.

Affected: Packagist: dompdf/dompdf

### Summary

dompdf accepts a BMP image and generates a PDF-compatible PNG based only on its *declared* header dimensions and never bounds width × height before the image is converted through GD. A 58-byte BMP whose header declares e.g. `6000×6000` is accepted and later drives `imagecreatetruecolor($width, $height)` (and PHP's native BMP decoder) to allocate the full pixel canvas. A payload can fit in a single HTTP request: the BMP can be inlined as a `data:image/bmp;base64,…` URI inside attacker-controlled HTML, so no upload, no remote fetch, and no chroot-reachable file is required. It was demonstrated that a **169-byte** request drove dompdf to render to **~412 MB peak RSS and ~4.8 s** of CPU/wall time, versus ~34 MB for an identically-sized benign request — roughly a 12× memory amplification per request, repeatable and unauthenticated.

### Details ## Root cause The image is processed based on declared dimensions and type alone — no pixel budget: ```php // src/Image/Cache.php:131-134 list($width, $height, $type) = Helpers::dompdf_getimagesize($resolved_url, $options->getHttpContext()); if (($width && $height && in_array($type, ["gif","png","jpeg","bmp","svg","webp"], true)) === false) { throw new ImageException("Image type unknown", E_WARNING); } ``` For BMPs that `getimagesize()` does not fully parse, dompdf trusts the raw header fields: ```php // src/Helpers.php:833-837 if (substr($data, 0, 2) === "BM") { $meta = unpack("vtype/Vfilesize/Vreserved/Vof…

Affected: Ubuntu:Pro:16.04:LTS: php-dompdf, Ubuntu:Pro:18.04:LTS: php-dompdf, Ubuntu:20.04:LTS: php-dompdf, Ubuntu:22.04:LTS: php-dompdf

Dompdf is an HTML to PDF converter for PHP. Versions 3.15 and prior accept a BMP image and generates a PDF-compatible PNG based only on its declared header dimensions and never bounds width × height before the image is converted through GD. A 58-byte BMP whose header declares e.g. 6000×6000 is accepted and later drives imagecreatetruecolor($width, $height) (and PHP's native BMP decoder) to allocate the full pixel canvas. A payload can fit in a single HTTP request: the BMP can be inlined as a data:image/bmp;base64,… URI inside attacker-controlled HTML, so no upload, no remote fetch, and no chroot-reachable file is required. I measured a 169-byte request driving a dompdf render to ~412 MB peak RSS and ~4.8 s of CPU/wall time, versus ~34 MB for an identically-sized benign request — roughly a 12× memory amplification per request, repeatable and unauthenticated. This issue has been fixed in version 3.16.