CVE-2025-55161

published 2025-08-11

CVE-2025-55161: Stirling-PDF is a locally hosted web application that performs various operations on PDF files. Prior to version 1.1.0, when using the…

Priority P1 80 critical 9.8 CVSS 3.1

AV N AC L PR N UI N S U C H I H A H

ITW EXPLOIT VulnCheck KEV

Stirling-PDF is a locally hosted web application that performs various operations on PDF files. Prior to version 1.1.0, when using the /api/v1/convert/markdown/pdf endpoint to convert Markdown to PDF, the backend calls a third-party tool to process it and includes a sanitizer for security sanitization which can be bypassed and result in SSRF. This issue has been patched in version 1.1.0.

Affected

2 ranges

Vendor	Product	Version range	Fixed in
stirling-tools	stirling-pdf	< 1.1.0	1.1.0
stirlingpdf	stirling_pdf	< 1.1.0	1.1.0

Detection & IOCs extracted from sources · hover to see the quote

url /api/v1/convert/markdown/pdf↗

sigma↗

shodan-query: http.title:"Stirling PDF"

• → Monitor for POST requests to /api/v1/convert/markdown/pdf containing Markdown image tags with external URLs (SSRF via img src), especially with multipart/form-data bodies and .md file uploads. ↗
• → Detect out-of-band DNS/HTTP interactions triggered by the server after receiving a crafted Markdown file upload — indicative of successful SSRF exploitation via this endpoint. ↗
• → A successful exploit response will return HTTP 200 with Content-Type application/pdf after submitting the malicious Markdown payload. ↗
• → Unauthenticated attackers can exploit this endpoint — no authentication headers are required in the attack request. ↗

• · The sanitizer intended to block SSRF can be bypassed; do not rely on the built-in sanitizer in pre-1.1.0 deployments as a security control. ↗

CVSS provenance

nvd v3.1 9.8 CRITICAL CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

vulncheck 8.6 HIGH

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