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Fencer Vulns
critical 9.8

CVE-2023-41330 json

Unsafe deserialization in knplabs/knp-snappy

published 2023-09-06 3 y ago modified 2026-09-10 1 mo ago also GHSA-92rv-4j2h-8mjj , EUVD-2023-2470

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
2.3%
EPSS 2.3% chance of exploitation in 30 days, percentile 83%
public exploits
0
none known

Summary

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.

Patch / fix

  • packagist knplabs/knp-snappy 1.4.3
  • knplabs snappy 1.4.3

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
total
Assessed
2 y ago

Exploit prediction

2.29% chance of exploitation in the next 30 days, higher than 83% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/KnpLabs/snappy/security/advisories/GHSA-92rv-4j2h-8mjj referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/KnpLabs/snappy/security/advisories/GHSA-gq6w-q6wh-jggc referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
GitHub 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
packagist knplabs/knp-snappy
<1.4.3
1.4.3

Affected products

  • KnpLabs snappy

Classification

Weakness
  • CWE-502 Deserialization of Untrusted Data

References

Sources

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