GHSA-x8g9-h984-pc36: PhpWeasyPrint vulnerable to SSRF and local file disclosure via the attachment option
Summary`pontedilana/php-weasyprint` fetches the content of option values server-side via `file_get_contents()` when the value looks like a URL, without restricting the URL scheme. The `attachment` option of `Pdf` is the reachable sink: any value that passes `isOptionUrl()` (`filter_var(..., FILTER_VALIDATE_URL)`) is downloaded by the PHP process and embedded into the generated PDF. Because `FILTER_VALIDATE_URL` accepts `http`, `https`, `ftp`, `file` and PHP stream wrappers such as `php://`, an attacker who can influence the `attachment` value reaches both a **Server-Side Request Forgery** primitive (e.g. internal HTTP endpoints, cloud metadata) and a **local file disclosure** primitive (`file://`, `php://filter/...`), with the fetched bytes exfiltrated as a PDF attachment.This is the same class of issue KnpLabs/snappy patched for its `xsl-style-sheet` option in [GHSA-c5fp-p67m-gq56](https://github.com/KnpLabs/snappy/security/advisories/GHSA-c5fp-p67m-gq56). The library is documented as a one-to-one substitute for KnpLabs/snappy and shares the same code shape.Affected versions`pontedilana/php-weasyprint` versions `<= 2.5.1`.Patched in: `2.6.0`.Privilege requiredAny caller that can influence the `attachment` option value handed to `Pdf::generate()` / `Pdf::getOutput()` / `setOption('attachment', ...)`. Typical reach paths: a value sourced from a request parameter, a per-tenant configuration row, or any user-controllable field that flows into the attachment list.Vulnerable code`src/Pdf.php` — `isOptionUrl()` accepts any well-formed URL regardless of scheme:`src/Pdf.php` — `handleArrayOptions()` fetches the URL content for the `attachment` option:`FILTER_VALIDATE_URL` returns truthy for `http://`, `https://`, `ftp://`, `file://localhost/...`, and `php://filter/...`, so `\file_get_contents()` is invoked on attacker-chosen schemes with no allow-list.Proof of conceptImpact**SSRF**: the server fetches arbitrary `http(s)`/`ftp` URLs, reaching internal-only services, link-local metadata endpoints, etc.**Local file / wrapper disclosure**: `php://filter/...` (and similar) let an attacker read and exfiltrate local file content inside the generated PDF.Affects any consumer that does not fully control the `attachment` option value.Note: passing a plain local path (e.g. `/etc/passwd`) or a `file://` path that resolves to an existing file is handled as a normal local attachment and is **not** the issue addressed here — that is the documented local-attachment feature (callers must not pass untrusted input to the option). The fix specifically removes the server-side fetch amplification through non-`http(s)` schemes.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N (6.5, Medium) — adjust `PR`/`S`/`A` to the consuming application's reachability (e.g. `PR:N` if the attachment value is reachable from an unauthenticated surface).CWE-918 (Server-Side Request Forgery); secondary CWE-22 (Improper Limitation of a Pathname) for the wrapper-based file read.Suggested fixRestrict the schemes the library will fetch to an allow-list (`http`, `https` by default), and treat any other scheme as inline content instead of fetching it:A value with a non-allowed scheme (`file://`, `php://`, `ftp://`, ...) is then never passed to `file_get_contents()`.CreditReported upstream to KnpLabs/snappy ([GHSA-c5fp-p67m-gq56](https://github.com/KnpLabs/snappy/security/advisories/GHSA-c5fp-p67m-gq56)); identified as applicable to `pontedilana/php-weasyprint`, which mirrors the same code.
CVSS v3.1: 6.5