CVE-2023-41330 Unsafe deserialization in knplabs/knp-snappy
Attacker can achieve remote code execution via PHAR deserialization bypass in KnpLabs Snappy library if they control filename input.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-41330?
CVE-2023-41330 is a critical unsafe deserialization vulnerability in KnpLabs snappy, published on 6 Sep 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-502
Which versions are affected by CVE-2023-41330?
2 open source packages ship an affected version, including knplabs/knp-snappy. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
knplabs/knp-snappy Packagist | All versions | 1.4.3 |
knplabs/knp-snappy Packagist | All versions | 1.4.3 |
Products include Knplabs Snappy.
How do I fix CVE-2023-41330?
Upgrade knplabs/knp-snappy to 1.4.3 or later.
Upgrade, and only deserialise data from trusted sources or with an allow-list of types. More about Unsafe deserialization.
Is CVE-2023-41330 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-41330 exists.
Other vulnerabilities in KnpLabs snappy
Sources
Also known as GHSA-92rv-4j2h-8mjj.