⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● Medium · CVSS 6.8

How to Fix CVE-2026-1301: Command Injection in Open62541

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

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 6.8 - Medium
Actively exploited?Not currently listed in CISA KEV
Affected1.5-rc1 < 1.5-rc2
Fixed inSee vendor advisory
Type (CWE)CWE-787: Out-of-bounds Write

What is CVE-2026-1301?

CVE-2026-1301 is an OS command injection bug in Open62541. 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: In builds with PubSub and JSON enabled, a crafted JSON message can cause the decoder to write beyond a heap-allocated array before authentication, reliably crashing the process and corrupting memory.

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 Open62541 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 Open62541'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-2026-1301

The fix is to upgrade Open62541 to version 1.5-rc2 or later.

Affected versions confirmed in the CVE record:

Patch via the OS package manager (Linux)


<!-- enrich_agent_2:v1 -->
# 1. Update the package metadata.
sudo apt update                                  # Debian / Ubuntu
sudo dnf check-update                            # RHEL / Rocky / AlmaLinux / Fedora
sudo zypper refresh                              # openSUSE

# 2. Pull the patched version `1.5-rc2` of Open62541 from o6 Automation GmbH.
sudo apt install --only-upgrade open62541
sudo dnf upgrade open62541
sudo zypper update open62541

# 3. Restart the affected service so the patched binary is the running binary.
sudo systemctl restart open62541 || true

# 4. Verify the running version.
open62541 --version

Verify the fix worked


<!-- enrich_agent_2:v1 -->
# 1. Confirm the running version matches the fixed-in version from the advisory.
#    Cross-check against the vendor advisory: https://www.cisa.gov/news-events/ics-advisories/icsa-26-036-03

# 2. Re-scan with your vulnerability scanner. The scanner should no longer flag
#    this CVE on the patched host.
# Example with Nmap NSE:
nmap -sV --script vuln <target-host>

# 3. Inspect the service / kernel logs for crash-loops or rollback events in
#    the first hour after the upgrade.
journalctl -u <service-name> --since "1 hour ago"
dmesg --since "1 hour ago"

If you cannot patch immediately

Restrict access to the management or affected endpoint at the network layer. If the vendor lists a configuration toggle that disables the vulnerable feature, use it until you can patch.

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 Open62541, 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-2026-1301 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-2026-1301?

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 Open62541 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.*