CVE-2023-41330

knplabs/knp-snappy is a PHP library allowing thumbnail, snapshot or PDF generation from a url or a html page. ## Issue On March 17th the vulnerability CVE-2023-28115 was disclosed, allowing an attacker to gain remote code execution through PHAR deserialization. Version 1.4.2 added a check `if (\strpos($filename, 'phar://') === 0)` in the `prepareOutput` function to resolve this CVE, however if the user is able to control the second parameter of the `generateFromHtml()` function of Snappy, it will then be passed as the `$filename` parameter in the `prepareOutput()` function. In the original vulnerability, a file name with a `phar://` wrapper could be sent to the `fileExists()` function, equivalent to the `file_exists()` PHP function. This allowed users to trigger a deserialization on arbitrary PHAR files. To fix this issue, the string is now passed to the `strpos()` function and if it starts with `phar://`, an exception is raised. However, PHP wrappers being case insensitive, this patch can be bypassed using `PHAR://` instead of `phar://`. A successful exploitation of this vulnerability allows executing arbitrary code and accessing the underlying filesystem. The attacker must be able to upload a file and the server must be running a PHP version prior to 8. This issue has been addressed in commit `d3b742d61a` which has been included in version 1.4.3. Users are advised to upgrade. Users unable to upgrade should ensure that only trusted users may submit data to the `AbstractGenerator->generate(...)` function.

• CWE-502

• https://github.com/KnpLabs/snappy/commit/d3b742d61a68bf93866032c2c0a7f1486128b67ePatch
• https://github.com/KnpLabs/snappy/security/advisories/GHSA-92rv-4j2h-8mjjExploit, Mitigation, Vendor Advisory
• https://github.com/KnpLabs/snappy/security/advisories/GHSA-gq6w-q6wh-jggcExploit, Vendor Advisory
• https://github.com/KnpLabs/snappy/commit/d3b742d61a68bf93866032c2c0a7f1486128b67ePatch
• https://github.com/KnpLabs/snappy/security/advisories/GHSA-92rv-4j2h-8mjjExploit, Mitigation, Vendor Advisory
• https://github.com/KnpLabs/snappy/security/advisories/GHSA-gq6w-q6wh-jggcExploit, Vendor Advisory

Published

Sep 6, 2023

Last Modified

Jun 17, 2026

Status

Modified

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