GHSA-2fmj-p74r-3wjm PhpWeasyPrint vulnerable to PHAR deserialization via output filename (CVE-2023-28115 case-insensitive bypass)

• Packagist pontedilana/php-weasyprint: < 2.6.0 → fixed in 2.6.0

Summary `pontedilana/php-weasyprint` guarded the output filename against the `phar://` stream wrapper with a case-sensitive blacklist: ```php if (0 === \strpos($filename, 'phar://')) { throw new \InvalidArgumentException('The output file cannot be a phar archive.'); } ``` PHP stream wrappers are case-insensitive, so `PHAR://`, `Phar://`, etc. bypass the check and reach `fileExists()` (`file_exists()`) in `prepareOutput()`. On PHP 7 (which the library still supports — PHP 7.4+), this triggers deserialization of a crafted PHAR archive's metadata, leading to remote code execution. This is the patch-bypass of CVE-2023-28115. The same issue and fix were handled upstream in KnpLabs/snappy (GHSA-92rv-4j2h-8mjj). Affected versions `pontedilana/php-weasyprint` versions `generateFromHtml('POC', 'PHAR://exploit.phar'); // On PHP /tmp/exploit is created ``` Impact • Remote code execution and filesystem access through PHAR metadata deserialization on PHP < 8, when the output filename is attacker-influenced and a PHAR can be planted. CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H (8.1, High) — Critical in deployments running PHP 7 with an upload surface; adjust to your environment. CWE-502 (Deserialization of Untrusted Data). Suggested fix Replace the case-sensitive blacklist with a scheme allow-list (`file` / no scheme), comparing the lowercased scheme parsed from the filename: ```php protected const ALLOWED_PROTOCOLS = ['file']; protected function isProtocolAllowed(string $filename): bool { if (false === $parsed = \parse_url($filename)) { throw new \InvalidArgumentException('The filename is not valid.'); } $protocol = isset($parsed['scheme']) ? \strtolower($parsed['scheme']) : 'file'; // ...special-case Windows drive letters (C:\...) as 'file'... return \in_array($protocol, self::ALLOWED_PROTOCOLS, true); } ``` `prepareOutput()` then rejects any non-`file` scheme (`phar`, `PHAR`, `php`, `http`, ...) before `file_exists()` is reached. Credit Original vulnerability and patch-bypass reported upstream to KnpLabs/snappy by Rémi Matasse of Synacktiv (GHSA-92rv-4j2h-8mjj); identified as applicable to `pontedilana/php-weasyprint`, which mirrors the same code.