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CVE-2018-18320: An issue was discovered in the Merlin.PHP component 0.6.6 for Asuswrt-Merlin devices

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CRITICAL 9.8REMOTEUPGRADEUPGRADEUPGRADE

CVE-2018-18320 is a critical-severity flaw (CVSS 9.8) affecting rt-ac5300 firmware, rt ac1900p firmware, rt-ac68u firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in the Merlin.PHP component 0.6.6 for Asuswrt-Merlin devices. An attacker can execute arbitrary commands because exec.php has a popen call. NOTE: the vendor indicates that Merlin.PHP is designed only for use on a trusted intranet network, and intentionally allows remote code execution

Why this priority

  • Critical severity
  • EPSS top 7%: very likely to be exploited
  • Public exploit reference
  • Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score9.8 (Critical)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance5.2% (top 7%)
CISA exploited listNo
Published2018-10-15
Last modified2026-06-17
Publisher (CNA): MITRE · Vendor: asuswrt-merlin project

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Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

asuswrt-merlin project rt-ac5300 firmware UPGRADE
Affected: <= 380.70
Fixed in: newer than 380.70
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
asuswrt-merlin project rt ac1900p firmware UPGRADE
Affected: <= 380.70
Fixed in: newer than 380.70
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
asuswrt-merlin project rt-ac68u firmware UPGRADE
Affected: <= 380.70
Fixed in: newer than 380.70
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
asuswrt-merlin project rt-ac68p firmware UPGRADE
Affected: <= 380.70
Fixed in: newer than 380.70
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
asuswrt-merlin project rt-ac88u firmware UPGRADE
Affected: <= 380.70
Fixed in: newer than 380.70
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
asuswrt-merlin project rt-ac66u b1 firmware UPGRADE
Affected: <= 380.70
Fixed in: newer than 380.70
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2018-18320?

rt-ac5300 firmware: upgrade to newer than 380.70; rt ac1900p firmware: upgrade to newer than 380.70; rt-ac68u firmware: upgrade to newer than 380.70. Exact commands for each OS are on this page.

Is CVE-2018-18320 being exploited?

CVE-2018-18320 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2018-18320 affect?

CVE-2018-18320 affects rt-ac5300 firmware, rt ac1900p firmware, rt-ac68u firmware. Severity is critical (CVSS 9.8). An issue was discovered in the Merlin.PHP component 0.6.6 for Asuswrt-Merlin devices. An attacker can execute arbitrary commands because exec.php has a popen call. NOTE: the vendor indicates that Merlin.PHP is designed only for use on a tru

How urgent is CVE-2018-18320?

Priority 67/100. Critical severity; EPSS top 7%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

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