CVE-2023-41330 is a critical-severity (CVSS 9.8) Deserialization of Untrusted Data vulnerability in knplabs/knp-snappy. 2 public exploit references exist, 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
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
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2023-41330 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
knplabs/knp-snappyReal-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
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | knplabs/knp-snappy | all versions | 1.4.3composer require knplabs/knp-snappy:^1.4.3 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
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.
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.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-41330 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-41330. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2023-41330 in your dependencies?
O3 Security finds CVE-2023-41330 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.