CVE-2026-26221
Unauthenticated .NET Remoting deserialization flaw in Hyland OnBase Timer Service enabling RCE.
Is CVE-2026-26221 being exploited?
Not confirmed. CVE-2026-26221 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 1.2% probability of exploitation in the next 30 days.
How severe is CVE-2026-26221?
CVE-2026-26221 is rated Critical with a CVSS score of 10.0. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-26221?
Not known from our data. No patch reference has been recorded for CVE-2026-26221, which is not the same as no patch existing — a fix may have shipped without a tagged reference, or after this record was written. The vendor advisory is the only authority on whether a fix exists, and mitigations may be available regardless.
What does CVE-2026-26221 affect?
CVE-2026-26221 affects Hyland OnBase Workflow Timer Service (NTService). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-26221?
Limit exposure to Timer Service; monitor SMB/NTLM; patch when available.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution via unsafe object unmarshalling; attacker can read/write files and trigger SMB/NTLM coercion.
Immediate action required
- affected>= 8.0 and <= 17.0.0
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.