CVE-2026-85217

Executive Summary

CVE-2026-85217 is a vulnerability in Autodesk Fusion Desktop (CWE-15, External Control of System or Configuration Setting) in which a maliciously crafted add-in can silently modify persistent network proxy settings when installed and executed, without user notification or consent. The flaw is rated 8.6 (High) under CVSS 3.1, with high confidentiality and integrity impact and a Scope change. It primarily affects workstation users of Fusion Desktop who install third-party add-ins; successful exploitation can redirect authenticated Fusion network traffic through an attacker-controlled proxy, exposing sensitive data associated with the current user session.

Technical Analysis

The NVD description states the core mechanism directly: a maliciously crafted add-in, when installed and executed in Autodesk Fusion Desktop, can modify persistent network proxy settings without user notification or consent. This is classified under CWE-15 (External Control of System or Configuration Setting), which describes a product that allows an external source to influence or control a configuration or setting that should be protected from tampering.

In this case, the affected setting is the persistent network proxy configuration used by the application. The technical essence of CWE-15 is that a trust boundary is crossed: data or control from an untrusted source (a third-party add-in) is applied to a configuration resource without adequate validation, authorization, or user consent. Because Fusion Desktop add-ins are executed within the context of the desktop application, an add-in that can reach the proxy-setting configuration surface can alter it persistently — meaning the change survives beyond the add-in's immediate execution.

The specific code paths, function names, configuration keys, registry locations, or file paths involved are NOT described in the NVD data provided. Consequently, no such identifiers are asserted here. What can be stated with confidence from the description alone is:

• The attack surface is the add-in installation and execution model of Autodesk Fusion Desktop.
• The externally influenced resource is the persistent network proxy setting.
• The action occurs without user notification or consent, indicating an absence of an authorization or consent gate for proxy-setting modification by add-ins.
• The affected setting is persistent, not session-scoped, so proxy redirection may affect subsequent network activity.

The CVSS vector CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H informs the analysis materially:

• AV:L (Attack Vector: Local) — exploitation requires local access to the target host, consistent with installing and running an add-in on a workstation rather than exploiting a remote network service.
• AC:L (Attack Complexity: Low) — no specialized conditions beyond the described scenario are required.
• PR:N (Privileges Required: None) — the attacker does not need elevated privileges on the target host.
• UI:R (User Interaction: Required) — a user must install and execute the malicious add-in, which is the delivery bottleneck.
• S:C (Scope: Changed) — the impact crosses from the vulnerable application into other security contexts/components, consistent with altering a system-wide or shared proxy setting that can affect traffic beyond Fusion itself.
• C:H / I:H / A:H — high confidentiality, integrity, and availability impact. High confidentiality/integrity align with traffic interception and redirection; the high availability rating is notable and may reflect dependence of network-dependent functionality on the altered proxy configuration.

The combination of AV:L and UI:R means this is not a wormable or remotely unauthenticated network exploit; it is a local, user-assisted supply-chain-style risk delivered through the add-in ecosystem.

Exploitation Scenarios

The following chain is derived strictly from the NVD description and the CWE-15 class. No specific function names, endpoints, registry keys, or file paths are invented, because none are provided in the source data. No public PoC is available; the chain below is an inference from the vulnerability class.

1. Reconnaissance / target identification. An attacker identifies users or organizations running Autodesk Fusion Desktop who are willing or accustomed to installing third-party add-ins. The add-in ecosystem itself is the reconnaissance surface — the attacker positions a crafted add-in where a Fusion user may encounter or install it.

2. Triggering the flaw class (CWE-15). The user installs and executes the maliciously crafted add-in in Fusion Desktop. Upon execution, the add-in influences the persistent network proxy configuration. Per the description, this happens without user notification or consent — there is no consent gate intercepting the configuration change. The trigger is therefore the execution of the add-in itself, which yields external control over a configuration setting.

3. Payload / execution method (class level). The "payload" is the configuration modification: the proxy setting is altered so that Fusion network traffic is routed through an attacker-controlled proxy. Because the setting is persistent, the redirection is not confined to a single session. At the class level, this is an unauthorized configuration-write operation performed by code that should not possess the authority to make it.

4. Post-exploitation impact. Authenticated Fusion network traffic can be redirected through the attacker-controlled proxy, potentially exposing sensitive information accessible with the current user. Because the traffic is authenticated as the victim user, an adversary controlling the proxy may observe, and depending on the transport, potentially alter, data flowing to and from Fusion services. The Scope:Changed rating indicates effects extend beyond the Fusion application proper.

Caveats and unknowns: The precise transport, the exact proxy-setting storage location, any cryptographic protections on the setting, and whether the attacker can decrypt or merely observe traffic are NOT specified in the available data and are not asserted here. No exploit code, PoC, or Nuclei template is known to exist for this CVE at the time of writing.

Impact Assessment

• Confidentiality (C:H): The stated risk is exposure of "sensitive information" associated with the current user. Redirecting authenticated traffic through an attacker-controlled proxy places the confidentiality of that traffic at risk.
• Integrity (I:H): Proxy manipulation can enable transparent modification of affected traffic, and the persistent configuration change itself is an integrity violation of system/application state.
• Availability (A:H): Rated high; altered proxy settings can disrupt or deny network-dependent functionality.
• Scope (S:C): Impact crosses scope, i.e., the compromise of the add-in execution context affects components beyond the immediate vulnerable component.
• Attack Vector / Privileges / Interaction: Local vector, no privileges required, but user interaction (install + execute the add-in) is required. This reduces mass-exploitation potential but is realistic in environments where add-ins are routinely trusted and installed.

Business impact / blast radius. The primary blast radius is individual Fusion Desktop workstations and the user-context data traversing Fusion network connections. Organizations in engineering, manufacturing, and design workflows using Fusion should treat third-party add-ins as untrusted code. Because AV is Local, enterprise-wide compromise does not occur through a single remote exploit; instead, the risk propagates through the add-in distribution channel (supply-chain-style). The absence of a patch (0/4 confidence) and absence of a CISA KEV listing indicate no confirmed widespread exploitation, but also no vendor remediation currently available to close the gap.

Detection Guidance

Sigma Rule

This rule detects installation or execution of unusual Autodesk Fusion add-ins and proxy-configuration changes associated with the user context. It is behavioral and does not rely on fabricated file paths.

title: Potential CVE-2026-85217 - Autodesk Fusion Add-in Proxy Tampering
id: 8f3c1a2e-5b47-4d9a-9c31-7f2e0a6b1d55
status: experimental
description: Detects execution of Autodesk Fusion add-in related processes coinciding with persistent network proxy configuration changes, consistent with CWE-15 external control of a configuration setting (CVE-2026-85217).
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-85217
author: valtersit.com threat intelligence
date: 2026/01/01
tags:
  - attack.t1553
  - attack.t1112
  - attack.t1090
logsource:
  category: process_creation
  product: windows
detection:
  selection_fusion:
    Image|endswith:
      - '\Fusion360.exe'
      - '\Fusion.exe'
  selection_proxy_change:
    CommandLine|contains:
      - 'proxy'
      - 'ProxyServer'
      - 'ProxyEnable'
      - 'netsh winhttp set proxy'
  condition: selection_fusion and selection_proxy_change
fields:
  - Image
  - CommandLine
  - ParentImage
  - User
falsepositives:
  - Legitimate enterprise proxy configuration by administrators
  - Fusion native proxy configuration via official UI
level: medium

YARA Rule

This YARA rule hunts for add-in artifacts referencing proxy manipulation. It matches on strings only; it does not assume specific file paths that are not provided in the source data.

rule CVE_2026_85217_Fusion_Addin_ProxyTamper
{
    meta:
        description = "Detects Autodesk Fusion add-in artifacts that reference persistent proxy configuration manipulation (CVE-2026-85217, CWE-15)"
        author = "valtersit.com threat intelligence"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-85217"
        date = "2026-01-01"
        severity = "high"

    strings:
        $addin1 = "Fusion" ascii wide nocase
        $addin2 = "add-in" ascii wide nocase
        $addin3 = "addin" ascii wide nocase
        $proxy1 = "ProxyEnable" ascii wide nocase
        $proxy2 = "ProxyServer" ascii wide nocase
        $proxy3 = "ProxyOverride" ascii wide nocase
        $proxy4 = "proxy" ascii wide nocase
        $net1   = "winhttp" ascii wide nocase
        $net2   = "Internet Settings" ascii wide nocase

    condition:
        filesize < 10MB and
        (2 of ($addin*)) and
        (2 of ($proxy*) or 1 of ($net*))
}

Suricata IDS Rule

Because the proxy redirection is a local configuration change, network detection focuses on the resulting traffic hairpinning to unexpected proxy destinations from the Fusion user context.

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-85217 Possible Autodesk Fusion Traffic Via Unauthorized Proxy"; flow:established,to_server; http.user_agent; content:"Fusion"; nocase; http.header; content:"Via"; nocase; classtype:trojan-activity; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-85217; sid:8521701; rev:1;)

Elastic Detection

This EQL rule correlates Fusion process execution with proxy configuration registry modification by the same process tree.

sequence by host.id, user.id with maxspan=2m
  [ process where process.name : "Fusion*.exe" ]
  [ registry where registry.path : "*\\Internet Settings\\*" and
      registry.value : ("ProxyServer", "ProxyEnable", "ProxyOverride") ]

Splunk SPL Query

Detects Fusion execution followed by or coinciding with proxy-setting modification events and unexpected outbound proxy connections.

index=main (source=XmlWinEventLog:Microsoft-Windows-Sysmon/Operational OR source=WinEventLog:Security)
(EventCode=1 Image="*\\Fusion*.exe")
OR (EventCode=13 RegistryKey="*\\Internet Settings\\*" RegistryValueName IN ("ProxyServer","ProxyEnable","ProxyOverride"))
OR (EventCode=3 DestinationPort IN (3128,8080,8888))
| eval risk=case(
    match(Image,"Fusion") AND match(CommandLine,"proxy"), "HIGH",
    match(RegistryKey,"Internet Settings"), "MEDIUM",
    true(), "LOW")
| stats count values(Image) values(CommandLine) values(RegistryKey) by host user risk
| where risk IN ("HIGH","MEDIUM")
| sort - count

Wazuh OSSEC Rule

Detects proxy configuration changes and Fusion add-in-related activity on Windows endpoints via Sysmon and registry monitoring.

<group name="autodesk_fusion,cve_2026_85217,">
  <rule id="852170" level="10">
    <if_sid>61613</if_sid>
    <field name="win.eventdata.targetObject">\\Internet Settings\\Proxy</field>
    <description>CVE-2026-85217: Persistent network proxy setting modified (possible Fusion add-in tampering, CWE-15)</description>
    <mitre>
      <id>T1112</id>
      <id>T1553</id>
    </mitre>
  </rule>

  <rule id="852171" level="8">
    <if_sid>61603</if_sid>
    <field name="win.eventdata.image">Fusion</field>
    <field name="win.eventdata.commandLine">proxy</field>
    <description>CVE-2026-85217: Autodesk Fusion process referencing proxy configuration</description>
    <mitre>
      <id>T1090</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source). No affected version range or vendor fix has been published in the available data. The following guidance is therefore precautionary and configuration-based.

1) Immediate mitigations

• Treat all third-party Fusion Desktop add-ins as untrusted code. Restrict add-in installation to an approved allowlist and require review before deployment.
• Monitor endpoint registry and configuration changes to persistent network proxy settings, particularly changes originating from Fusion or add-in execution contexts.
• Enforce enterprise proxy configuration via managed policy (e.g., Group Policy / MDM) so user- or application-level proxy changes are overridden and detected.
• Alert on outbound traffic from Fusion workstation hosts to unexpected proxy ports (3128, 8080, 8888) or to non-approved proxy endpoints.
• Where feasible, restrict the privileges and network configuration access available to add-in processes.

2) Patch / upgrade steps

• No vendor patch is currently available (patch confidence 0/4). Monitor Autodesk's security advisories and the NVD entry for CVE-2026-85217 for a fixed release.
• Once a patched Fusion Desktop version is published, stage and deploy it to all affected endpoints, prioritizing hosts where third-party add-ins are used.
• Because no affected version range is provided, inventory all deployed Fusion Desktop versions and apply vendor updates as they are released.

3) Long-term hardening

• Adopt a signed, vetted add-in policy and validate add-in provenance before installation.
• Centralize and lock down network proxy configuration for all engineering workstations.
• Implement egress filtering so workstations cannot silently route authenticated application traffic through arbitrary external proxies.
• Log and retain process creation, registry, and network telemetry for Fusion hosts to support retrospective detection.
• Include third-party application add-in ecosystems in supply-chain risk reviews.

References

• NVD — CVE-2026-85217: https://nvd.nist.gov/vuln/detail/CVE-2026-85217
• CWE-15 — External Control of System or Configuration Setting: https://cwe.mitre.org/data/definitions/15.html
• Autodesk Security Advisories / Trust Center: https://www.autodesk.com/trust/security-advisories
• CISA Known Exploited Vulnerabilities Catalog (CVE-2026-85217 NOT listed as of this report): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Threat actor / exploitation status: No public proof-of-concept, exploit code, or Nuclei template is known for CVE-2026-85217. The CVE is not listed in CISA KEV, and no exploit-in-the-wild or threat-actor campaign has been reported in the provided data. The report reflects the state of available intelligence at the time of writing; absence of public exploitation does not preclude private or targeted abuse of the add-in supply chain.