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CRITICAL ADOBE WARNING: Attackers Can Take Over Your PC Just By Opening a PDF File (Patch NOW)

Deep Technical Analysis of CVE-2025-64785, CVE-2025-64899, CVE-2025-64786, and CVE-2025-64787

TL;DR

Adobe Reader and Adobe Acrobat have been found vulnerable to four high-impact security flaws that allow attackers to take full control of Windows and macOS systems with no user interaction other than opening a malicious PDF file. The vulnerabilities include:

CVE-2025-64785 — CWE-426 — Untrusted Search Path — Arbitrary Code Execution (Critical 7.8)
CVE-2025-64899 — CWE-125 — Out-of-Bounds Read → Arbitrary Code Execution (Critical 7.8)
CVE-2025-64786 — CWE-347 — Improper Verification of Cryptographic Signature (Moderate 3.3)
CVE-2025-64787 — CWE-347 — Improper Verification of Cryptographic Signature (Moderate 3.3)

Attackers can craft a malicious PDF that triggers unsafe DLL loading, memory corruption, or bypasses digital signature warnings. This allows malware, ransomware loaders, banking trojans, and remote access implants to execute silently on the victim’s system.

If Adobe Reader or Acrobat is not patched immediately, opening the wrong PDF can result in complete system takeover.

1. Executive Summary

Adobe Reader and Adobe Acrobat remain two of the most widely deployed desktop applications in the world, embedded into business workflows, financial operations, legal document systems, healthcare infrastructures, and consumer devices. Because they handle untrusted documents from email, messaging apps, and websites, attackers consistently target Adobe PDF vulnerabilities to gain privileged access to victim machines.

The four vulnerabilities analyzed in this advisory represent a highly dangerous combination:

Two Critical RCE Flaws that allow remote code execution simply by opening a PDF
Two Signature Verification Bypass Flaws that disable Adobe’s warning system

These flaws enable PDF-based exploits to execute malicious code, evade security prompts, and deploy implants or ransomware before the user realizes anything is wrong. PDF documents are trusted by default—making them one of the most effective vectors for enterprise compromise.

This is a high-risk national and enterprise-level security exposure requiring immediate patching.

2. Understanding PDF Exploitation in 2025

Modern PDF files support JavaScript execution, embedded multimedia, custom object streams, launch actions, XFA forms, 3D objects, and dozens of complex internal structures. These powerful features provide attackers with multiple opportunities to exploit:

Memory corruption
DLL loading pathways
Signature validation routines
Reader sandbox escapes
Privilege escalation paths

Over the past decade, the vast majority of high-profile cyberattacks involving document delivery were conducted via:

Malicious PDF payloads
Zero-day font or rendering engine vulnerabilities
Embedded JavaScript that triggers RCE
Packed PDFs that evade antivirus detection

PDF exploitation now forms part of the core tradecraft of APT groups, ransomware operators, financial fraud syndicates, and nation-state campaigns. These new Adobe vulnerabilities extend that threat even further.

3. Overview of the Four Adobe Vulnerabilities

The four CVEs disclosed impact PDF handling in different layers:

CVE	CWE	Category	Impact	Severity	CVSS
CVE-2025-64785	CWE-426	Untrusted Search Path	Arbitrary Code Execution	Critical	7.8
CVE-2025-64899	CWE-125	Out-of-Bounds Read	Arbitrary Code Execution	Critical	7.8
CVE-2025-64786	CWE-347	Crypto Signature Verification Bypass	Security Feature Bypass	Moderate	3.3
CVE-2025-64787	CWE-347	Crypto Signature Verification Bypass	Security Feature Bypass	Moderate	3.3

Individually, each vulnerability poses a risk. Combined, they create a catastrophic attack chain capable of bypassing warnings, loading malicious libraries, and executing arbitrary code with full privileges.

4. Deep Dive: CVE-2025-64785 — Untrusted Search Path

CVE-2025-64785 is a critical vulnerability in Adobe Reader/Acrobat’s DLL loading mechanism. When Adobe Reader opens a PDF that references external modules or resources, it searches multiple system paths to locate required libraries.

The vulnerability arises when Adobe prioritizes directories controlled by the attacker over secure system paths—allowing a malicious DLL to be loaded.

How Attackers Exploit It

Craft a PDF that contains an embedded reference to a legitimate Adobe DLL name.
Package a malicious DLL with the PDF (via ZIP, email, or installer-like structure).
Place Adobe in a state where it loads the DLL from the local directory.
Adobe mistakenly loads the attacker DLL instead of the system DLL.

No warning is shown to the user.

Impact

Execution of arbitrary code
Deployment of ransomware loaders
Execution of keyloggers or banking malware
Persistence mechanisms using Adobe startup hooks

5. Deep Dive: CVE-2025-64899 — Out-of-Bounds Read → RCE

This vulnerability involves a memory corruption flaw in Adobe’s PDF rendering engine. When parsing specially crafted PDF objects, Adobe performs an out-of-bounds read that can leak memory, expose program state, or be chained into arbitrary code execution.

Exploitation Path

PDF contains malformed object streams with manipulated offsets.
The rendering engine reads outside valid memory boundaries.
Exposed memory reveals ASLR offsets or key security values.
Attacker uses this leak to perform ROP (Return-Oriented Programming).
Final stage payload executes inside the Adobe Reader process.

Why This Is Deadly

Memory corruption vulnerabilities in PDF engines have historically been used by APT groups and exploit brokers. Once memory is exposed:

ASLR defeats become trivial
ROP payloads can be executed reliably
Sandbox escapes become achievable

This vulnerability forms the core RCE capability in the attack chain.

6. Deep Dive: CVE-2025-64786 / CVE-2025-64787 — Signature Verification Bypass

Digital signature validation is one of Adobe’s last lines of defence. When a PDF contains macros, JavaScript, or embedded executables, Adobe normally warns users if the signature is invalid.

These two vulnerabilities weaken that system by failing to validate:

Certificate chains
Metadata integrity
Certain signature formats

Attackers can therefore create PDFs that appear trusted, signed, or “secure” to the end user—even when they contain malware.

Impact

Users open malicious PDFs without suspicion
Organizations bypass scanning due to “trusted document” status
Security appliances may skip inspection

This allows the Critical RCE vulnerabilities to execute silently.

7. Combined PDF Attack Chain

When these four CVEs are chained together, the attack becomes extremely effective:

Attacker crafts a malicious PDF that contains malformed objects, external library references, and misleading signature metadata.
Victim opens the PDF—triggering memory corruption or DLL loading.
CVE-2025-64899 leaks memory and bypasses ASLR.
CVE-2025-64785 loads malicious DLL from attacker directory.
CVE-2025-64786/87 hide warnings by bypassing cryptographic checks.
Final payload executes silently inside Adobe Reader.

No additional clicks are required. No prompts are shown. This is a true “open-and-own” zero-click PDF exploitation path.

8. Attack Flow Diagrams

             Victim Opens PDF
                     |
                     v
       +----------------------------+
       | PDF Engine Begins Parsing  |
       +----------------------------+
                     |
                     | Malformed Object Stream
                     v
       +----------------------------+
       | CVE-2025-64899 Triggered   |
       | Memory Leak / OOB Read     |
       +----------------------------+
                     |
                     | Info Leak Enables ROP
                     v
       +----------------------------+
       | CVE-2025-64785 Triggered   |
       | Untrusted DLL Loaded       |
       +----------------------------+
                     |
                     | Malicious Code Execution
                     v
       +----------------------------+
       | CVE-2025-64786/87          |
       | Signature Bypass Hides     |
       | Security Warnings          |
       +----------------------------+
                     |
                     v
              Full System Takeover

9. Real-World Exploitation Scenarios

9.1 Business Email Compromise (BEC)

Attackers send an “invoice” PDF containing the exploit. Accounting staff open it. Ransomware deploys instantly.

9.2 Government Targeting

Malicious PDFs embedded in meeting agendas or regulatory forms bypass detection using the signature validation flaws.

9.3 Supply Chain Attack

Vendors send compromised PDFs disguised as compliance documents to customers, infecting entire supply chains.

9.4 Banking and Financial Fraud

Attackers send fake KYC forms with malicious payloads to gain remote access to financial systems.

10. Global & Enterprise Impact

These vulnerabilities impact:

Windows and macOS users
Enterprises deploying Adobe Reader at scale
SaaS businesses relying on PDF workflows
Legal and finance teams handling sensitive documents
Healthcare systems processing digital prescriptions

Because PDF is the world’s default document format, the attack surface is enormous.

11. Which Systems Are Most at Risk?

Unpatched Adobe Reader DC and Acrobat installations
Windows machines with insecure DLL search paths
macOS devices relying on outdated Adobe versions
Organizations without endpoint protection
Users who download PDFs from email or messaging apps

12. Early Indicators & Detection Opportunities

Unexpected Adobe Reader child processes
DLL loads from non-standard directories
Large or malformed PDF object streams
JavaScript execution inside PDFs
Crashes in Adobe Reader upon opening certain files

13. Recommended Security Tools

End of PART 1. Continue to PART 2 for the full detection engineering suite, mitigation steps, Sigma/YARA rules, IR plan, patch matrix, JSON-LD schema, and final commentary.

14. MITRE ATT&CK Mapping

Technique	ID	Relevance
Victim Delivered Malicious File	T1204.002	Malicious PDF delivered via email or messaging.
User Execution	T1204	Trigger occurs when PDF is opened.
Exploitation for Client Execution	T1203	Memory corruption and RCE via Adobe Reader.
DLL Search Order Hijacking	T1574.002	CVE-2025-64785 enables malicious DLL loading.
Obfuscated/Encrypted Files	T1027	Used to hide PDF exploit layers.
Credential Access via Keylogging	T1056.001	Post-exploitation payloads often include keyloggers.
Exfiltration Over Web Services	T1567	Stolen data transmitted to C2 servers.

15. STRIDE Threat Model

Applying STRIDE to the Adobe PDF attack chain:

S — Spoofing: Signature bypass CVEs allow malicious PDFs to appear trustworthy.
T — Tampering: Memory corruption enables modification of Adobe process memory.
R — Repudiation: Bypassed logging if Adobe crashes silently.
I — Information Disclosure: Out-of-bounds reads leak sensitive data.
D — Denial of Service: Crashes Adobe Reader instantly in some cases.
E — Elevation of Privilege: Malicious DLL loading enables system-level execution.

16. Sigma Detection Rules

16.1 Detect Untrusted DLL Loading by Adobe Reader

title: Adobe Reader Untrusted DLL Load
id: cdb-adobe-dll-hijack-2025-1
status: experimental
logsource:
  product: windows
  category: image_load
detection:
  selection:
    ImageLoaded|endswith: '.dll'
    Image: '*AcroRd32.exe'
    ImageLoaded|contains:
      - 'AppData'
      - 'Temp'
      - 'Downloads'
  condition: selection
fields:
  - Image
  - ImageLoaded
level: high

16.2 Detect Adobe Reader Launching Suspicious Child Processes

title: Adobe PDF Exploit – Suspicious Child Process
id: cdb-adobe-child-proc-2025-1
status: experimental
logsource:
  product: windows
  category: process_creation
detection:
  parent:
    ParentImage: '*AcroRd32.exe'
  child:
    Image|contains:
      - 'cmd.exe'
      - 'powershell.exe'
      - 'wscript.exe'
  condition: parent and child
level: critical

17. YARA Rules

17.1 YARA Rule for Malicious PDF Object Streams

rule CDB_PDF_Exploit_ObjectStream
{
    meta:
        description = "Detects malicious PDF object streams associated with memory corruption"
        author = "CyberDudeBivash"
        year = "2025"

    strings:
        $objstm = "/ObjStm"
        $js1 = "/JavaScript"
        $launch = "/Launch"
        $mal1 = "stream\x0a\x78\x9c"
        $xref = "xref"
        $oob = "%%EOF"

    condition:
        uint16(0) == 0x2550 and
        ( $objstm or $js1 or $launch ) and $mal1 and $xref
}

17.2 YARA Rule for DLL Hijack Payloads

rule CDB_Adobe_DLLHijack
{
    meta:
        description = "Detect malicious DLLs used in Adobe hijacking chain"
        author = "CyberDudeBivash"

    strings:
        $s1 = "AdobeReader"
        $s2 = "DllMain"
        $e1 = { 6A 00 6A 00 68 ?? ?? ?? ?? E8 }

    condition:
        ($s1 and $s2) or $e1
}

18. Suricata Signatures

alert http any any -> any any (
    msg:"CDB Adobe Exploit PDF Delivery";
    content:"%PDF";
    http_client_body;
    pcre:"/ObjStm|JavaScript|Launch/i";
    classtype:attempted-user;
    sid:202564785;
    rev:1;
)

19. SOC Playbook: First 1–24 Hours

19.1 First 1 Hour

Identify user who opened suspicious PDF.
Collect Adobe logs (crashes, sandbox violations).
Isolate endpoint immediately.

19.2 First 6 Hours

Scan for malicious DLLs in user directories.
Check for unusual Adobe child processes.
Search SIEM for exploitation indicators.

19.3 First 24 Hours

Rotate credentials of impacted users.
Block malicious hashes, domains, URLs.
Deploy YARA & Sigma scans across endpoints.

20. Incident Response Plan (30 / 60 / 90 Days)

30 Days

Complete forensic investigation of impacted devices.
Patch all Adobe products organization-wide.

60 Days

Deploy enterprise DLP & EDR enhancements.
Roll out mandatory secure document training.

90 Days

Include PDF exploitation testing in red-team exercises.
Audit and improve DLL trust path policies.

21. Patch Matrix

Product	Patched Version	Status
Adobe Reader DC (Windows)	2025.002 or later	Patch Required
Adobe Acrobat Pro (Windows)	2025.003 or later	Patch Required
Adobe Reader (macOS)	2025.001 or later	Patch Required

22. Enterprise Mitigation Guidance

Disable JavaScript in Adobe Reader enterprise-wide.
Restrict Adobe from loading external DLLs using GPO/AppLocker.
Block PDF execution from email temp folders.
Implement robust EDR capable of scanning PDF object streams.
Enforce automatic Adobe updates via enterprise patch management.

23. Indicators of Compromise (IOCs)

Suspicious File Artifacts

DLL files found in Downloads/AppData next to PDFs
PDFs with multiple /ObjStm streams
Unexpected encrypted PDF elements

Process IOCs

AcroRd32.exe spawning cmd.exe or powershell.exe
Adobe Reader sandbox escapes

24. Final CyberDudeBivash Commentary

The combination of these four Adobe vulnerabilities forms one of the most dangerous document-based exploitation chains seen in recent years. PDF files remain one of the most trusted and widely exchanged file formats, making them an ideal weapon for attackers.

Organizations must immediately patch Adobe Reader and Acrobat, deploy robust monitoring, and restrict high-risk PDF functionalities. Business workflows depending on document exchange must now treat every untrusted PDF as a potential system compromise.

This incident is another reminder: PDF is no longer a “safe document format.” It is a fully capable attack surface.

#CyberDudeBivash #AdobeZeroDay #PDFExploit #CVE2025 #CyberSecurity #MalwareAnalysis #ExploitResearch #ThreatIntel #IncidentResponse #EnterpriseSecurity