⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● High · CVSS 8.6

How to Fix CVE-2026-25857: Command Injection in Tenda G300-F

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

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 8.6 - High
Actively exploited?Not currently listed in CISA KEV
Affected0 <= 16.01.14.2
Fixed inSee vendor advisory
Type (CWE)CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

What is CVE-2026-25857?

CVE-2026-25857 is an OS command injection bug in Tenda G300-F. The product builds a shell command from untrusted input without escaping, so injected metacharacters run as the service account, often root or SYSTEM. Vendor description: Tenda G300-F router firmware version 16.01.14.2 and prior contain an OS command injection vulnerability in the WAN diagnostic functionality (formSetWanDiag). The implementation constructs a shell command that invokes curl and incorporates attacker-controlled input into the command line without adequate neutralization.

Why this CVE matters

Command injection in a network appliance or management console gives the attacker the same privileges as the service account, which is usually root or SYSTEM. From there, persistence, lateral movement, and credential theft follow with off-the-shelf tooling.

For deployments of Tenda G300-F 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 Tenda G300-F'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-2026-25857

  1. Read the vendor advisory in full: https://blog.evan.lat/blog/cve-2026-25857/
  2. Upgrade Tenda G300-F to the patched build listed in the vendor advisory.
  3. Back up the configuration (and database, where applicable) before upgrading.
  4. Rotate any credentials, API keys, or session tokens that the vulnerable service touched. An unauthenticated RCE-class flaw means anything the process could see should be treated as exposed.
  5. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
  6. Restart the affected service so the patched binary loads, then verify the new version (see verification section).

Patched-version commands

Vendor advisory: https://blog.evan.lat/blog/cve-2026-25857/

Affected: Tenda G300-F: 0 <= 16.01.14.2

Patched in: 16.01.14.2


# Vendor advisory: https://blog.evan.lat/blog/cve-2026-25857/
# Affected: Tenda G300-F: 0 <= 16.01.14.2
# Patched in: 16.01.14.2

# Debian / Ubuntu.
sudo apt update
sudo apt install --only-upgrade tenda-g300-f
dpkg -s tenda-g300-f | grep -i version

# RHEL / Rocky / AlmaLinux / Fedora.
sudo dnf upgrade tenda-g300-f
rpm -q tenda-g300-f

# openSUSE.
sudo zypper update tenda-g300-f

# Verify the running version matches 16.01.14.2 from the advisory.
tenda-g300-f --version 2>/dev/null || true


# Windows: pull the latest cumulative updates that include this CVE's fix.
Install-Module PSWindowsUpdate -Force -SkipPublisherCheck -Confirm:$false
Get-WindowsUpdate -AcceptAll -Install -AutoReboot
Get-HotFix | Sort-Object InstalledOn -Desc | Select-Object -First 5

Verify the fix landed


# Vendor advisory: https://blog.evan.lat/blog/cve-2026-25857/
# Post-patch verification (replace <service> with the real service unit).
journalctl -u <service> --since "10 minutes ago"
dmesg --since "10 minutes ago"

# Re-scan with your vulnerability scanner (Nessus, Qualys, Tenable, OpenVAS).
# It should no longer flag CVE-2026-25857 on the patched target.

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 Tenda G300-F, 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-2026-25857 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-2026-25857?

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.

Do I need to assume compromise if my Tenda G300-F was internet-facing and unpatched?

For an unauthenticated RCE-class flaw exposed to the public internet during the known exploitation window, yes. Review logs, rotate credentials the process could access, and look for unexpected accounts, scheduled tasks, or outbound connections.

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.*