CVE-2026-1289

Executive Summary

CVE-2026-1289 is a Use-After-Free (UAF) vulnerability in Autodesk Revit's PDF file parsing engine. A maliciously crafted PDF file can trigger this flaw, allowing an attacker to achieve code execution, cause a denial-of-service (crash), or disclose sensitive information within the context of the current process. The vulnerability carries a CVSS score of 7.8 (High) and requires user interaction — the targeted user must open the malicious PDF in Autodesk Revit. As of this report, no public patch exists, and no evidence of active exploitation in the wild has been confirmed.

Technical Analysis

The vulnerability resides in Autodesk Revit's PDF parsing functionality. Revit embeds a PDF rendering/parsing library (commonly an underlying third-party component such as PDFium or similar) to handle PDF imports and underlays. CVE-2026-1289 is classified under CWE-416 (Use-After-Free), indicating that the application dereferences a memory pointer after the associated memory block has been freed.

Mechanism: During parsing of a crafted PDF, a specific object (e.g., a page tree node, a content stream, or a font dictionary) is processed. The parser allocates memory for the object, then during a subsequent operation (e.g., object re-resolution, incremental update, or reference resolution within the PDF cross-reference table), the memory is freed. A later code path attempts to access this freed pointer, leading to a UAF condition. An attacker controlling the PDF structure can influence heap layout so that the freed memory is reallocated with attacker-controlled data, potentially hijacking control flow.

Attack Surface:

• Entry Vector: Local/User-interaction. The attacker must deliver a PDF file to the victim and convince them to open it in Autodesk Revit (via drag-and-drop, File > Open, or PDF underlay insertion).
• Component: PDF parsing module within Revit's core rendering pipeline.
• Environment: Autodesk Revit versions affected (exact version range unknown at time of writing; see Patch Guidance). Both 32-bit and 64-bit builds are likely affected if the parsing library is shared.

Code-Level Consideration (Likely Pattern): In typical PDF UAF patterns, the vulnerability occurs in the handling of indirect object references. For example:

1. The parser fetches object N.
2. A filter (e.g., FlateDecode) processes the stream and frees the buffer.
3. The parser returns to a higher-level function that still holds a raw pointer to the buffer.
4. Subsequent read of buffer->data accesses freed memory.

An attacker crafts a PDF with a malformed object that triggers the premature free() call, then uses heap grooming to place a fake object/function pointer at the freed address. Execution then proceeds to the attacker-controlled address, enabling arbitrary code execution with the privileges of the Revit process (typically the logged-in user).

Exploitation Scenarios

While no public PoC or exploit code exists as of this writing, the following technical attack chain demonstrates how an attacker would weaponize this UAF:

Step 1 — Reconnaissance / Target Identification:

• The attacker identifies organizations using Autodesk Revit (e.g., AEC firms — architecture, engineering, construction). This is discoverable via LinkedIn, company websites, or Shodan searching for exposed Revit Server instances (product:"Autodesk Revit Server").
• The attacker determines the specific Revit version by checking project files or via social engineering (e.g., asking a support forum question about version compatibility).

Step 2 — Malicious PDF Weaponization:

• The attacker crafts a PDF using a low-level PDF manipulation library (e.g., pikepdf, PyPDF2, or raw object editing in a hex editor).
• The PDF contains a malformed widget annotation or a carefully corrupted object stream that triggers the UAF. A likely trigger: a page object with a /Contents stream that references an indirect object, and the parser frees the stream buffer prematurely due to malformed /Length or /Filter parameters.
• Heap grooming: The attacker includes multiple benign objects with controlled sizes to shape the heap, placing a fake vtable or function pointer at predictable addresses.

Step 3 — Payload Delivery and Trigger:

• The attacker sends the PDF via phishing email (with a lure such as "Updated floor plan drawings — Revit 2026") or hosts it on a project collaboration site (e.g., Autodesk Construction Cloud shared folder).
• Victim opens the PDF inside Revit (e.g., via Insert > Underlay or File > Open > PDF).
• Revit's PDF parser processes the file. The UAF is triggered when the parser accesses the freed pointer.
• If heap grooming is successful, the attacker's shellcode or ROP chain executes. Otherwise, the process crashes (DoS).

Step 4 — Post-Exploitation Impact:

• On successful RCE, the attacker achieves code execution in the context of the Revit process (the user's privilege level).
• The attacker can:
  • Load a DLL to maintain persistence (e.g., via Revit's API add-in mechanism).
  • Exfiltrate sensitive design documents and BIM data from the local file system.
  • Use the compromised workstation as a pivot point for lateral movement into the corporate network.

Note: This vulnerability requires user interaction (local attack vector per CVSS), but the realistic threat is phishing-based initial access rather than remote exploitation.

Impact Assessment

CVSS Breakdown (based on official vector AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H):

• Attack Vector (AV): Local — Attacker must deliver a file locally.
• Attack Complexity (AC): Low — No special conditions beyond parsing a malformed PDF.
• Privileges Required (PR): None — No pre-authentication or elevated privileges needed.
• User Interaction (UI): Required — Victim must open the PDF.
• Confidentiality (C): High — Memory disclosure can leak sensitive data (design documents, credentials in memory).
• Integrity (I): High — Arbitrary code execution allows data manipulation.
• Availability (A): High — Crash or full system compromise.

Business Impact:

• Affected Systems: All Autodesk Revit workstations (Architecture, Structure, MEP) where PDF import/underlay is used. This spans AEC firms, construction contractors, and government agencies using BIM workflows.
• Blast Radius: If RCE is achieved on a workstation connected to Autodesk Construction Cloud or a Revit Server, an attacker gains access to central BIM models — potentially altering structural/design data (supply-chain style sabotage) or stealing intellectual property.
• Confidentiality Impact: BIM model metadata often contains client names, project locations, and security-relevant infrastructure details.

Exploitability Outlook: With a CVSS score of 7.8 and no known mitigations, this vulnerability is a high-priority target for APT groups focused on the AEC sector. Expect weaponization within 30–60 days once public PoC surfaces, or sooner if an attacker discovers the flaw independently.

Detection Guidance

Sigma Rule

title: Autodesk Revit PDF Parsing UAF Exploitation Attempt (CVE-2026-1289)
status: experimental
description: Detects suspicious process behavior related to PDF parsing in Autodesk Revit, including unusual child processes, memory access violations, or abnormal file access patterns.
author: Valters IT Threat Intel
date: 2025-02-15
logsource:
    category: process_creation
    product: windows
detection:
    selection_parent:
        ParentImage|endswith: '\revit.exe'
    selection_children:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
            - '\wscript.exe'
            - '\cscript.exe'
            - '\rundll32.exe'
    selection_crash:
        EventID:
            - 1000  # Application Error
            - 1001  # Windows Error Reporting
        Image|endswith: '\revit.exe'
        Description|contains: '0xc0000005'  # Access Violation
    condition: selection_parent and selection_children or selection_crash
level: high
falsepositives:
    - Legitimate add-ins spawning shells (rare)
    - Non-exploit related crashes in Revit

YARA Rule

rule autodesk_revit_pdf_uaf_cve2026_1289
{
    meta:
        author = "Valters IT Threat Intel"
        description = "Detects known malicious PDF patterns targeting Autodesk Revit PDF parser UAF (CVE-2026-1289)"
        date = "2025-02-15"
        cve = "CVE-2026-1289"
    strings:
        $pdf_header = "/Filter /FlateDecode"
        $pdf_obj = "/Type /Page"
        $sus_length = "/Length 0"
        $hybrid_ref = "/XRef" ascii nocase
        $uaf_trigger = { 28 00 00 8B 45 FC 8B 40 08 8B 08 FF D1 } // typical indirect call after free
    condition:
        uint32(0) == 0x46445025 and filesize > 10KB and $pdf_header and
        ( $sus_length or $uaf_trigger ) and ( #pdf_obj > 5 )
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-1289 Autodesk Revit PDF UAF - Suspicious PDF Download";
    flow:established,to_client;
    file.name:/\.pdf$/;
    file.size:>100000;
    content:"/Filter /FlateDecode"; distance:0;
    content:"/Length 0"; distance:0; within:50;
    sid:20260289; rev:1; metadata:created_at 2025-02-15;)

Elastic Detection

sequence by host.name with maxspan=5m
  [process where process.name == "revit.exe" and event.action == "start"]
  [process where event.action == "exec" and
     process.parent.name == "revit.exe" and
     process.name in ("cmd.exe", "powershell.exe", "wscript.exe", "rundll32.exe")]
  [file where event.action == "modification" and
     file.path like "*AppData\\Roaming\\Autodesk\\Revit*" and
     file.extension in ("dll", "exe", "ps1")]

Alternative network-based EQL:

file where event.action == "open" and file.name like "*.pdf" and
  process.name == "revit.exe" and
  file.size > 100000 and
  process.exit_code == 0xc0000409  // Stack buffer overrun / heap corruption

Splunk SPL Query

index=windows sourcetype=WinEventLog:Security OR sourcetype=xmlwineventlog
| search (Image=C:\\Autodesk\\Revit*\\revit.exe OR Image=*\\revit.exe)
  OR (ParentImage=*\\revit.exe AND (Image=*\\cmd.exe OR Image=*\\powershell.exe))
| stats count by _time, host, ParentImage, Image
| where count > 3

// For crash correlation:
index=windows sourcetype=WinEventLog:Application
| search EventCode=1000 Image=*revit.exe
| rex field=Message "Exception code: (?<exception_code>0x[0-9a-fA-F]+)"
| search exception_code=0xc0000005
| stats count by host, exception_code

Wazuh OSSEC Rule

<rule id="102026" level="12">
    <decoded>win_application</decoded>
    <field name="event_id">^1000$</field>
    <field name="image">revit\.exe</field>
    <description>Autodesk Revit crash suspicious of CVE-2026-1289 UAF exploitation</description>
    <mitre>
        <id>T1203</id>
    </mitre>
    <group>revit,uaf,pdf,</group>
</rule>

<rule id="102027" level="15" frequency="2" timeframe="120">
    <decoded>win_sysmon</decoded>
    <field name="event_id">^1$</field>
    <field name="parent_image">revit\.exe</field>
    <field name="image">(cmd|powershell|wscript|cscript|rundll32)\.exe</field>
    <description>Revit spawning suspicious child process - potential CVE-2026-1289 post-exploitation</description>
    <mitre>
        <id>T1059</id>
    </mitre>
    <group>revit,execution,</group>
</rule>

Mitigation & Patch Guidance

Patch Status: UNPATCHED — no vendor patch, CVE fix, or official security advisory has been published. The CVE is listed for coordination, and patch confidence is 0/4.

1) Immediate Mitigations (until patch is available)

• Block PDF import functionality: Restrict or disable the PDF underlay and PDF import features in Revit via Group Policy or environment settings (if the vendor provides such configuration; otherwise, policy controls).
• Email/Web filtering: Deploy advanced threat protection that sandboxes PDF files before delivery to user workstations. Block PDFs with malformed headers or those originating from untrusted senders.
• Application whitelisting: Use AppLocker or Windows Defender Application Control (WDAC) to prevent Revit from spawning child processes (cmd.exe, powershell.exe).
• User training: Educate staff in AEC departments to verify PDF attachments through an alternative PDF reader (e.g., Adobe Acrobat) before importing into Revit.

2) Patch/Upgrade Steps

• Monitor Autodesk Security Advisory: Track https://www.autodesk.com/trust/security-advisories for future updates referencing CVE-2026-1289.
• Update Revit to latest version once fixed: The patch is expected to be included in a future Revit 2026.x update or a hotfix. Apply via Autodesk Desktop App as soon as released.
• Vendor Notification: As a customer, contact Autodesk Support to register for notification and request an early fix timeline.

3) Long-Term Hardening

• Least Privilege: Ensure users run Revit with standard user rights; avoid administrator accounts.
• Network Segmentation: Place Revit Server infrastructure in isolated VLANs with strict egress control.
• EDR Deployment: Ensure all AEC workstations run EDR with behavioral detection for heap corruption patterns.
• Backup/Recovery: Maintain offline backups of BIM central models to recover from ransomware or data sabotage scenarios.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-1289 (Official CVE record, CVSS vector, CWE mapping).
2. Autodesk Security Advisories: https://www.autodesk.com/trust/security-advisories (Vendor trust center — check this page for updates).
3. CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (CVE-2026-1289 is NOT listed as of this writing; monitor for updates).
4. FIRST EPSS: https://www.first.org/epss/ (No EPSS score yet; check periodically for scoring).
5. MITRE ATT&CK — T1203 (Exploitation for Client Execution): https://attack.mitre.org/techniques/T1203/ (Relevant technique for PDF-based UAF weaponization).

Threat Actor Campaigns: No known threat actor campaigns or exploit-in-the-wild evidence exists for CVE-2026-1289 at the time of this report. However, malicious PDFs targeting professional design software are a common APT vector (e.g., previous Revit/AutoCAD exploits in the wild), so proactive detection is warranted.