CVE-2026-33436: stirling pdf Input Validation Flaw

Description

Stirling-PDF is a locally hosted web application that facilitates various operations on PDF files. In versions prior to 2.0.0, file upload endpoints render user-supplied filenames directly into HTML using unsafe methods like innerHTML without sanitization. An attacker can craft a file with a malicious filename containing JavaScript that executes in the uploading user's browser context, resulting in reflected XSS. The issue affects numerous upload endpoints across the application. The issue has been fixed in version 2.0.0.

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CVSS v3.1 Score

3.1

LOW

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N

EPSS — Exploit Prediction

0.0008

Probability of exploitation

0.24%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-20 Improper Input Validation

CWE-79 Cross-site Scripting (XSS)

CWE-116 CWE-116

Affected Products

Vendor	Product	Versions
stirlingpdf	stirling_pdf	< 2.0.0

References

Advisories & Patches

https://github.com/Stirling-Tools/Stirling-PDF/security/advisories/GHSA-q5j3-4m5w-wp75 https://github.com/Stirling-Tools/Stirling-PDF/security/advisories/GHSA-q5j3-4m5w-wp75

Exploits

https://github.com/Stirling-Tools/Stirling-PDF/security/advisories/GHSA-q5j3-4m5w-wp75 https://github.com/Stirling-Tools/Stirling-PDF/security/advisories/GHSA-q5j3-4m5w-wp75

Frequently Asked Questions

What is CVE-2026-33436? +

Stirling-PDF is a locally hosted web application that facilitates various operations on PDF files. In versions prior to 2.0.0, file upload endpoints render user-supplied filenames directly into HTML using unsafe methods like innerHTML without sanitization. An attacker can craft a file with a malicious filename containing JavaScript that executes in the uploading user's browser context, resulting in reflected XSS. The issue affects numerous upload endpoints across the application. The issue has been fixed in version 2.0.0. It has a CVSS v3.1 base score of 3.1 (LOW).

How severe is CVE-2026-33436? +

CVE-2026-33436 has a CVSS v3.1 score of 3.1 out of 10, rated LOW. This is a low-severity vulnerability with limited impact. The EPSS score is 0.0008, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-33436? +

CVE-2026-33436 affects products from stirlingpdf, specifically: stirling_pdf. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-33436? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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