A serious security flaw, tracked as CVE-2024-30279, has been found in Adobe Acrobat Reader versions 20.005.30574, 24.002.20736, and earlier. This vulnerability allows attackers to execute arbitrary code on your computer, just by convincing you to open a specially crafted PDF file. This exploit happens through what's called an "out-of-bounds write", letting attackers overwrite critical parts of your memory and take control.

In this article, we break down how CVE-2024-30279 works, show how an attack can happen, and provide code snippets, mitigation tips, and links to the most important references.

What is an Out-of-Bounds Write?

Out-of-bounds write vulnerabilities occur when a program writes data outside the allocated buffer's boundaries. In Acrobat Reader's case, a crafted PDF can cause the software to write data past the end of an internal memory buffer, potentially overwriting data that controls program execution.

24.002.20736 and earlier

Adobe's official security bulletin:
APSB24-26: Security Updates Available for Adobe Acrobat and Reader

Attack Scenario: How Does Exploitation Work?

1. Attacker crafts a malicious PDF file that takes advantage of the vulnerable code in Adobe Reader.

Victim opens the malicious PDF (usually received via email or downloaded from the web).

3. Malicious code executes in the context of the current user, giving the attacker control—possibly installing malware, stealing data, or more.

Exploitation requires user interaction: nothing happens unless you open the infected document.

Technical Details

Adobe hasn't released all technical details, but security researchers and the patch diffing community have shed some light on what happens.

The Problem: Processing a certain PDF element (e.g., a filter in an image object) causes the program to write data past the end of an expected buffer when the PDF is malformed in a certain way.

Here is a simplified example showing the vulnerability pattern in pseudo-code

// UNSAFE CODE PATTERN (Simplified for Illustration)
void vulnerable_function(char *input, int size) {
    char buffer[256];
    for (int i = ; i < size; i++) {
        buffer[i] = input[i];
    }
}

If size is greater than 256, this code writes past the end of buffer, possibly overwriting critical stack data.

In the real Acrobat Reader bug, the attacker controls data within the PDF, and the software copies this data to a buffer without properly checking the size.

Proof-of-Concept: Triggering the Crash

While responsible disclosure prevents the release of dangerous live exploits, security researchers often make *harmless* code or document snippets that demonstrate a crash (without executing malicious code).

Example: PoC PDF with Crafted Stream

The PDF object below (in actual PoC PDFs) might look like this

2  obj
<< /Length 256
   /Filter [/FlateDecode /MaliciousFilter]
>>
stream
...payload bytes...
endstream
endobj

Here, /MaliciousFilter is not a real filter but is crafted to confuse the Reader’s parsing logic, causing it to write past the end of an internal buffer.

Opening such a file in an unpatched Acrobat Reader may cause a crash or even a code execution event, depending on the payload.

Here's a conceptual Python snippet for generating a "crasher" PDF

pdf_content = """
%PDF-1.4
2  obj
<< /Length 300
   /Filter [/FlateDecode /BadFilter]
>>
stream
""" + "A" * 400 + """
endstream
endobj

xref
 3
000000000 65535 f 
000000001 00000 n 
0000000073 00000 n 
trailer
<< /Root 1  R >>
startxref
500
%%EOF
"""

with open("cve-2024-30279-crash.pdf", "w") as f:
    f.write(pdf_content)

NOTE: This PoC is not weaponized and is purely for crash demonstration.

Update Acrobat Reader immediately to the latest version

- Get the latest version from Adobe

Adobe Security Bulletin (APSB24-26):

https://helpx.adobe.com/security/products/acrobat/apsb24-26.html

NVD Entry for CVE-2024-30279:

https://nvd.nist.gov/vuln/detail/CVE-2024-30279

Security Research Twitter Thread (diffing):

Example Thread

For developers, compare patched vs. unpatched versions to see how size checks and input filtering were added after discovery.

Summary

CVE-2024-30279 is a dangerous vulnerability in Adobe Acrobat Reader that could allow an attacker to take over your computer—just by getting you to open a prefabricated PDF. Luckily, Adobe has patched this issue, but it's crucial to update now, avoid suspicious files, and teach others about the danger.

Stay safe, update your software, and help others stay informed!


*This exclusive post is for educational awareness and helping users understand current risks in the wild. Please do not use this information irresponsibly.*

Timeline

Published on: 05/23/2024 09:15:08 UTC
Last modified on: 06/04/2024 17:39:22 UTC