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Deserialization of Untrusted DataWeakness · CWE-502

CVE-2026-26221

CRITICAL · 9.8 CVSS v3.1 Published 2026-02-13
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Hyland OnBase contains an unauthenticated .NET Remoting exposure in the OnBase Workflow Timer Service (Hyland.Core.Workflow.NTService.exe). An attacker who can reach the service can send crafted .NET Remoting requests to default HTTP channel endpoints on TCP/8900 (e.g., TimerServiceAPI.rem and TimerServiceEvents.rem for Workflow) to trigger unsafe object unmarshalling, enabling arbitrary file read/write. By writing attacker-controlled content into web-accessible locations or chaining with other OnBase features, this can lead to remote code execution. The same primitive can be abused by supplying a UNC path to coerce outbound NTLM authentication (SMB coercion) to an attacker-controlled host.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Hyland OnBase Workflow Timer Service exposes an unauthenticated .NET Remoting interface on TCP/8900 with unsafe object unmarshalling. Attackers can send crafted requests to TimerServiceAPI.rem and TimerServiceEvents.rem endpoints to achieve arbitrary file read/write, potentially leading to RCE via web-accessible directories or SMB coercion via UNC path injection.

MitigationImmediately restrict network access to TCP/8900 via firewall/segmentation, apply vendor-provided patches for Hyland OnBase, and disable .NET Remoting if not required.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify Hyland OnBase Workflow Timer Service is running
    On Windows, open Services console (services.msc) and look for 'Hyland OnBase Workflow Timer Service' or check via PowerShell: Get-Service | Where-Object {$_.DisplayName -like '*OnBase*Workflow*Timer*'}. On Linux, check running processes for similar service names.
    Affected if The service is installed and running, exposing the attack surface.
  2. Confirm TCP port 8900 is listening
    Run 'netstat -an | findstr :8900' or 'Get-NetTCPConnection -LocalPort 8900' to check if the .NET Remoting interface is bound to a listening port.
    Affected if Port 8900 is in LISTENING state, indicating the vulnerable interface is active.
  3. Test .NET Remoting endpoint accessibility
    Use a tool like netcat or PowerShell Test-NetConnection to verify the TimerServiceAPI.rem and TimerServiceEvents.rem endpoints respond: nc -zv <target> 8900 or curl http://<target>:8900/TimerServiceAPI.rem (if HTTP tunneling is enabled).
    Affected if The endpoints respond, confirming the unauthenticated interface is reachable.
  4. Check OnBase installation version
    Inspect the OnBase installation directory for version information, typically found in registry at HKLM\SOFTWARE\Hyland\OnBase or in installation logs under the OnBase program files folder.
    Affected if The installed version falls within the vulnerable version range for this CVE.
  5. Review .NET Remoting configuration
    Examine the OnBase configuration files (typically .config XML files in the Workflow Timer Service installation directory) for <channel> elements registering TCP port 8900 and <remoteHub> or similar .NET Remoting settings.
    Affected if .NET Remoting is explicitly configured and enabled on TCP/8900.

A user is affected if the Hyland OnBase Workflow Timer Service is running with .NET Remoting enabled on TCP/8900, making the TimerServiceAPI.rem and TimerServiceEvents.rem endpoints reachable over the network.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Immediately restrict network access to TCP/8900 via firewall/segmentation, apply vendor-provided patches for Hyland OnBase, and disable .NET Remoting if not required.

Have this fixed Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,980
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-26221 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
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  • Version or environment caveats, and links to real fixes
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