Security readout for executives and security teams
Plain-English summary
This flaw can let an unauthenticated network attacker abuse Hyland OnBase Workflow Timer Service to read or write files and potentially execute code. Business risk is highest where the Timer Service is reachable beyond trusted administrative networks.
Executive priority
Treat as urgent for any Hyland OnBase environment using the affected Timer Service. Prioritize exposure reduction immediately, then follow Hyland’s bulletin for remediation.
Technical view
The issue is an unauthenticated .NET Remoting exposure in Hyland.Core.Workflow.NTService.exe. Reachable default HTTP channel endpoints on TCP/8900 can process crafted remoting requests, leading to unsafe object unmarshalling, arbitrary file read/write, possible RCE, and UNC-path NTLM coercion.
Likely exposure
Exposure appears limited to Hyland OnBase Workflow Timer Service version 8.0 identified in the source bundle. Systems are most exposed when TCP/8900 or the remoting endpoints are reachable from untrusted networks.
Exploitation context
The bundle does not cite CISA KEV listing or active exploitation. The vulnerability is still high urgency because it is network reachable, unauthenticated, low complexity, and can affect confidentiality, integrity, and availability.
Researcher notes
Evidence supports CWE-502 unsafe deserialization via .NET Remoting and notes arbitrary file read/write, RCE chaining, and SMB coercion. The bundle does not provide confirmed exploit-in-the-wild evidence or a specific patch version.
Mitigation direction
- Review Hyland bulletin OB2025-03 and apply vendor guidance.
- Restrict access to TCP/8900 to trusted hosts only.
- Remove internet or broad internal exposure for Timer Service endpoints.
- Check Hyland support channels for fixed versions or configuration mitigations.
- Monitor outbound NTLM authentication attempts from affected servers.
Validation and detection
- Inventory OnBase Workflow Timer Service deployments and versions.
- Confirm whether TCP/8900 is reachable from untrusted network segments.
- Review service configuration for TimerServiceAPI.rem and TimerServiceEvents.rem exposure.
- Check web-accessible directories for unexpected files or recent writes.
- Review logs for unusual remoting activity or outbound SMB authentication.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-502: Code execution behavior lookup
Code execution and unsafe deserialization weaknesses often justify reviewing execution behavior and process telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupFile access behavior lookup
The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-26221 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
2 official scoresWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N——VulnCheckVulnerability scoring details
Base CVSS 4.0 score
9.3CriticalVector: 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
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://www.hyland.com/en/solutions/products/onbaseCVE reference, VulnCheck · product
- https://community.hyland.com/resources/bulletins-and-notices/223223-security-update-onbase-workflow-timer-service-bulletin-ob2025-03CVE reference, VulnCheck · vendor-advisory, mitigation
- https://www.vulncheck.com/advisories/hyland-onbase-timer-services-unauthenticated-net-remoting-rceCVE reference, VulnCheck · third-party-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Deserialization of Untrusted Data
Deserialization of Untrusted Data represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.