CVE-2026-1288

Executive Summary

CVE-2026-1288 is a denial-of-service (DoS) vulnerability in Autodesk Revit, triggered when a maliciously crafted RFA file is converted to FormIt via the “Convert RFA to FormIt” feature. The flaw is a NULL Pointer Dereference (CWE-476) that causes the application to crash, leading to a temporary loss of service. With a CVSS score of 5.5 (Medium), the attack requires user interaction (opening a malicious file) and local access, but no special privileges. No public exploit code or proof-of-concept is currently available, and no patch has been released. The vulnerability is not related to any open-source package or WordPress ecosystem.

Supply Chain & Package Security

This vulnerability does not affect NPM, PyPI, Go, or Ruby packages. It is specific to Autodesk Revit, a proprietary desktop application.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
• Base Score: 5.5 (Medium)
• Attack Vector: Local (AV:L) – requires the attacker to deliver a malicious RFA file to the victim.
• Attack Complexity: Low (AC:L) – no special conditions needed.
• Privileges Required: None (PR:N) – no authentication needed.
• User Interaction: Required (UI:R) – victim must open the file and initiate conversion.
• Scope: Unchanged (S:U) – impact is confined to the vulnerable component.
• Confidentiality Impact: None (C:N)
• Integrity Impact: None (I:N)
• Availability Impact: High (A:H) – application crash leads to DoS.

Threat Level: Medium. Exploitation is straightforward but requires user interaction. No remote code execution or data breach is possible.

Deep Dive & Mechanics

The vulnerability resides in the RFA-to-FormIt conversion routine within Autodesk Revit. When a specially crafted RFA file is processed, the software fails to validate a pointer before dereferencing it, resulting in a NULL Pointer Dereference. This causes the application to crash, denying service to the user.

Root Cause: The conversion function does not check for null pointers returned by internal parsing routines when handling malformed RFA data. An attacker can craft an RFA file that triggers this condition.

Attack Vector: The attacker must deliver the malicious RFA file via email, download, or other means. The victim must then open the file in Revit and use the “Convert RFA to FormIt” feature.

Impact: Only availability is affected. The crash may result in loss of unsaved work but does not allow code execution or data theft.

Vulnerable vs. Patched Code

No patch is currently available. The vulnerable code is in the proprietary conversion module. A hypothetical fix would involve adding null-pointer checks before dereferencing pointers returned by parsing functions.

Vulnerable Code (Conceptual):

void ConvertRFAToFormIt(RFAFile *file) {
    DataBlock *block = ParseRFA(file);
    // No null check
    ProcessBlock(block);  // Crash if block is NULL
}

Patched Code (Conceptual):

void ConvertRFAToFormIt(RFAFile *file) {
    DataBlock *block = ParseRFA(file);
    if (block == NULL) {
        LogError("Invalid RFA file");
        return;
    }
    ProcessBlock(block);
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Autodesk Revit (any version with “Convert RFA to FormIt” feature)
• A malicious RFA file crafted to trigger NULL pointer dereference

Steps:

1. Craft a malicious RFA file using a hex editor or custom script. The file must contain malformed data that causes the conversion routine to return a NULL pointer.
2. Deliver the file to the victim (e.g., via email or file share).
3. Victim opens the file in Revit and selects “Convert RFA to FormIt”.
4. Revit crashes, causing denial of service.

Example (Conceptual):

# Craft a minimal RFA file with corrupted header
import struct
# RFA header (simplified)
header = b'\x00' * 100  # Malformed data
with open('malicious.rfa', 'wb') as f:
    f.write(header)

Note: No public exploit code exists. This is a conceptual demonstration.

Blue Team (Defense)

Detection:

• Monitor for unusual RFA files being opened or converted.
• Use file integrity monitoring to detect unexpected RFA files.
• Enable application crash logging in Revit.

Prevention:

• Restrict execution of Revit to trusted users only.
• Use application whitelisting to prevent untrusted Revit instances.
• Educate users not to open RFA files from untrusted sources.

Response:

• If a crash occurs, collect the RFA file and Revit crash dump for analysis.
• Block the malicious file hash at the perimeter.

Indicators of Compromise (IOCs)

• File Hashes: No known hashes (no public PoC).
• File Names: malicious.rfa or any RFA file from untrusted sources.
• Process Behavior: Revit.exe crashes with exception code 0xC0000005 (Access Violation) or 0xC0000374 (Heap Corruption).
• Event Logs: Windows Application Event Log may show Revit crash events with faulting module Revit.exe.

Detection Engineering

YARA Rule

rule CVE_2026_1288_RFA_NULL_PTR {
    meta:
        description = "Detects malicious RFA files exploiting CVE-2026-1288"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2026-1288"
    strings:
        $rfa_magic = { 52 46 41 }  // "RFA" magic bytes
        $null_trigger = { 00 00 00 00 00 00 00 00 }  // Potential null pointer trigger
    condition:
        $rfa_magic at 0 and #null_trigger > 5
}

Sigma Rule

title: CVE-2026-1288 Revit RFA Conversion Crash
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects Revit crashes caused by malicious RFA files
author: Valters IT
date: 2025-04-10
logsource:
    product: windows
    service: application
detection:
    selection:
        EventID: 1000
        Provider_Name: 'Application Error'
        Faulting_Module: 'Revit.exe'
        Exception_Code: '0xc0000005'
    condition: selection
falsepositives:
    - Legitimate Revit crashes due to other bugs
level: medium

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-1288 RFA File Transfer Detected"; flow:to_server; filemagic:"RFA"; content:"|52 46 41|"; depth:3; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

• Disable the “Convert RFA to FormIt” feature if not needed.
• Implement strict file validation for RFA files before conversion.
• Use application sandboxing to limit Revit’s impact on the system.

Long-Term Fix:

• Await an official patch from Autodesk.
• Monitor Autodesk security advisories for updates.

Workaround:

• Convert RFA files only from trusted sources.
• Use a dedicated virtual machine for processing untrusted RFA files.

Valters IT Signature This report was generated by Valters IT Cyber Threat Intelligence. For questions, contact intelligence@valters-it.com.