⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● Low · CVSS 2.7

How to Fix CVE-2026-1791: Unrestricted File Upload in Operation and Maintenance Security Gateway

Other vulnerabilities in the same area that are worth patching alongside this one:

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 2.7 - Low
Actively exploited?Not currently listed in CISA KEV
AffectedV5.5ST00001B113
Fixed inSee vendor advisory
Type (CWE)CWE-434: Unrestricted Upload of File with Dangerous Type

What is CVE-2026-1791?

CVE-2026-1791 is an unrestricted file upload flaw in Operation and Maintenance Security Gateway. An attacker can upload files of arbitrary type or to arbitrary locations, leading to webshell deployment and remote code execution. Vendor description: Unrestricted Upload of File with Dangerous Type vulnerability in Hillstone Networks Operation and Maintenance Security Gateway on Linux allows Upload a Web Shell to a Web Server.This issue affects Operation and Maintenance Security Gateway: V5.5ST00001B113.

Why this CVE matters

Unrestricted file upload is the classic webshell vector. The attacker uploads a script with an executable extension, then requests it through the same web server to execute commands.

For deployments of Operation and Maintenance Security Gateway that have been exposed to the public internet during the disclosure window, the operating assumption should be that scanning has already happened. Even where exploitation has not been publicly observed, scanning for the vulnerable fingerprint is cheap and routine. Patching closes the door; log review and credential rotation close out the rest of the response.

Am I affected?

You are affected if your installation matches any of these version ranges:

Check your installed version against the list above. If you cannot determine the version, treat the system as affected and follow the upgrade path below.

Open Operation and Maintenance Security Gateway's About dialog or run the vendor-documented version-check command. Compare the result against the affected ranges in the advisory.

How to fix CVE-2026-1791

  1. Read the vendor advisory in full: https://www.hillstonenet.com.cn/security-notification/2025/12/08/wgscld/
  2. Upgrade Operation and Maintenance Security Gateway to the patched build listed in the vendor advisory.
  3. Back up the configuration (and database, where applicable) before upgrading.
  4. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
  5. Restart the affected service so the patched binary loads, then verify the new version (see verification section).

Generic patch procedure


# Confirm the patched build against the vendor advisory: https://www.hillstonenet.com.cn/security-notification/2025/12/08/wgscld/
# 1. Identify the running version of Hillstone Networks Operation and Maintenance Security Gateway.
which operation-and-maintenance-security-gateway && operation-and-maintenance-security-gateway --version || true
dpkg -l | grep -i operation-and-maintenance-security-gateway || rpm -qa | grep -i operation-and-maintenance-security-gateway || true

# 2. Pull the patched build from the vendor's distribution channel.
#    Target: the build named in the vendor advisory

# 3. Apply per the vendor's documented upgrade procedure (installer / package
#    manager / firmware utility).

# 4. Restart the affected service so the patched binary loads.
sudo systemctl restart <service-name>

# 5. Confirm the running version matches the advisory's fixed build.
operation-and-maintenance-security-gateway --version


# Windows equivalent: pull current updates and confirm product version.
Install-Module -Name PSWindowsUpdate -Force -SkipPublisherCheck -Confirm:$false
Get-WindowsUpdate -AcceptAll -Install -AutoReboot
Get-CimInstance Win32_Product | Where-Object { $_.Name -match 'Operation and Maintenance Security Gateway' } |
  Select-Object Name, Version

Verify the fix landed


# Confirm the patched build against the vendor advisory: https://www.hillstonenet.com.cn/security-notification/2025/12/08/wgscld/
# 1. Confirm the running version equals the advisory's fixed-in build.
#    (Use the platform-specific version probe from the commands above.)

# 2. Re-scan with your vulnerability scanner (Nessus, Qualys, Tenable, OpenVAS).
#    The scanner should no longer flag CVE-2026-1791 on the patched target.

# 3. Inspect recent service and kernel logs for crash-loops or rollback events.
journalctl --since "10 minutes ago" | tail -200
dmesg --since "10 minutes ago" | tail -100

If you cannot patch immediately

Restrict access to the management interface to trusted internal IP addresses only. Block public access at the firewall and require VPN for any remote administration. Apply the patch as soon as a maintenance window allows.

How to verify the fix worked

If your installation was internet-reachable during the disclosure window, treat log review as part of the remediation rather than an optional follow-up. Look for unexpected administrator accounts in Operation and Maintenance Security Gateway, scheduled tasks or cron jobs you did not create, new files in web-accessible directories, and outbound connections to addresses not in your baseline. Suspicious requests to the vulnerable endpoint immediately followed by successful 200-class responses with unusually large bodies are a strong indicator of exploitation.

Frequently asked questions

Is CVE-2026-1791 being exploited in the wild?

Public exploitation has not been confirmed by CISA at the time of writing. Treat the patch as time-sensitive anyway; reports often lag actual abuse.

Will a WAF or IDS rule fully mitigate CVE-2026-1791?

No. Network-layer filters can reduce noise and slow opportunistic scanners, but they will not stop a determined attacker. The vendor patch is the only durable fix.

How long should I plan for the upgrade?

Typical vendor-documented upgrade windows for Operation and Maintenance Security Gateway run from a few minutes to under an hour depending on cluster size. Test in a staging environment first and follow the vendor's documented HA upgrade order.

References

*This guide was assembled from the official vendor advisory, the NVD record, and the CISA KEV catalog entry on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*