CVE-2026-0931: M-Files Server DoS Vulnerability

CVE-2026-0931 Overview

CVE-2026-0931 is a denial-of-service vulnerability affecting M-Files Server versions prior to 26.5.16015.3. An authenticated administrative user can trigger a condition that crashes the M-Files Server process. The service then fails to restart automatically, leaving the platform unavailable until manual intervention occurs.

The issue is classified under [CWE-1286] (Improper Validation of Syntactic Correctness of Input). The vulnerability is reachable over the network but requires high privileges, which limits practical exploitation to actors who already hold administrator credentials.

Critical Impact
A single authenticated admin request can halt M-Files Server availability and block automatic recovery, disrupting document management operations until an operator manually restores the service.

Affected Products

M-Files Server versions before 26.5.16015.3

Discovery Timeline

2026-08-05 - CVE-2026-0931 published to NVD
2026-08-05 - Last updated in NVD database

Technical Details for CVE-2026-0931

Vulnerability Analysis

CVE-2026-0931 is a denial-of-service defect in the M-Files Server process. An authenticated user with administrator privileges can send input that causes the server to crash. The process does not recover through automatic restart mechanisms, so availability is lost until an operator intervenes.

The vulnerability affects availability only. Confidentiality and integrity of stored data are not impacted according to the vendor advisory. The M-Files Security Advisory confirms the affected version range and identifies 26.5.16015.3 as the fixed release.

Root Cause

The root cause maps to [CWE-1286], improper validation of the syntactic correctness of input. M-Files Server accepts administrative input without sufficient validation, and a malformed value drives the process into an unrecoverable failure state. Because the service does not restart, the fault propagates from a transient crash into a sustained outage.

Attack Vector

The attack vector is network-based. An attacker must authenticate to M-Files Server with an administrator account before issuing the malformed request. There is no user interaction requirement beyond the authenticated session. The high privilege requirement constrains the threat model to insider misuse, compromised administrator credentials, or lateral movement scenarios where an attacker has already gained privileged access.

No public proof-of-concept exploit code is available. The vulnerability is described in prose by the vendor. Refer to the M-Files Security Advisory for vendor-provided technical detail.

Detection Methods for CVE-2026-0931

Indicators of Compromise

Unexpected termination of the M-Files Server process with no accompanying automatic restart.
Administrator-authenticated API or client requests immediately preceding a service crash.
Extended M-Files Server downtime requiring manual service start by an operator.

Detection Strategies

Monitor Windows Service Control Manager events for M-Files Server stop events that are not correlated with planned maintenance windows.
Correlate administrator authentication events with subsequent process crashes to identify request patterns that precede failures.
Alert on gaps in M-Files Server application telemetry that indicate the process is no longer running.

Monitoring Recommendations

Enable and forward M-Files Server application and audit logs to a centralized logging platform for retention and correlation.
Track administrator account activity and flag unusual API request patterns from privileged sessions.
Configure availability monitoring against the M-Files Server endpoint to detect outages within seconds of a crash.

How to Mitigate CVE-2026-0931

Immediate Actions Required

Upgrade M-Files Server to version 26.5.16015.3 or later on all production and staging deployments.
Audit the set of accounts holding M-Files administrator privileges and remove any that are unnecessary.
Enforce multi-factor authentication on all administrator accounts to reduce the risk of credential-based abuse.

Patch Information

M-Files has released version 26.5.16015.3, which remediates CVE-2026-0931. Administrators should apply the update following the guidance in the M-Files Security Advisory. Verify the running server build after upgrade to confirm the fixed version is in place.

Workarounds

Restrict network access to the M-Files Server administrative interface using firewall rules or VPN gating until the patch is applied.
Configure the M-Files Server Windows service recovery options to attempt automatic restart on failure, reducing outage duration if a crash occurs.
Limit administrator account issuance to a minimal set of trusted operators and rotate credentials for any accounts that may have been exposed.

bash

# Configure Windows service recovery to auto-restart M-Files Server after failure
sc.exe failure "MFServer" reset= 86400 actions= restart/60000/restart/60000/restart/60000
sc.exe qfailure "MFServer"