CVE-2026-49260: php-weasyprint: shell command injection via configurable WeasyPrint binary path due to inverted is_executable() guard (mirror of KnpLabs/snappy GHSA-vpr4-p6fq-85jc)

pontedilana/php-weasyprint builds the shell command for WeasyPrint by passing the binary path through escapeshellarg() first and then checking the quoted result with is_executable(). On POSIX escapeshellarg('/usr/local/bin/weasyprint') returns '/usr/local/bin/weasyprint' with the single-quote characters as part of the string, so is_executable() looks for a file whose actual name includes those quotes. That file never exists, the “safe” branch is dead code, and the raw $binary string (set via the constructor or setBinary()) flows directly into Symfony\Component\Process\Process::fromShellCommandline(). Any deployment whose binary path is sourced from configuration, an environment variable, or a per-tenant setting reaches a shell-command-injection sink. The library is documented as a one-to-one substitute for KnpLabs/snappy and inherited the exact pre-fix codepath KnpLabs patched in GHSA-vpr4-p6fq-85jc (Snappy 1.7.1).