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Vulnerability record · CVE-2026-26221 · published 13 February 2026

CVE-2026-26221: Deserialization of untrusted data vulnerability

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.

9.3 CVSS 4.0 Critical EPSS 1.4% · top 28.4% CWE-502 · Deserialization of untrusted data Deferred
9.3CVSS 4.0 base score
1.4%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
17 Jun 2026Last modified by NVD

Description

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://community.hyland.com/resources/bulletins-and-notices/223223-security-update-onbase-workflow-timer-service-bullet
https://www.hyland.com/en/solutions/products/onbase
https://www.vulncheck.com/advisories/hyland-onbase-timer-services-unauthenticated-net-remoting-rce

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Source: NIST National Vulnerability Database (record CVE-2026-26221), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.