CVE-2018-8879: Stack-based buffer overflow in Asuswrt-Merlin firmware for ASUS devices older than 384.4 and ASUS firmware bef

Q: How do I fix CVE-2018-8879?

rt-ac66u firmware: upgrade to 3.0.0.4.382.50470. Exact commands for each OS are on this page.

Q: Is CVE-2018-8879 being exploited?

CVE-2018-8879 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2018-8879 affect?

CVE-2018-8879 affects rt-ac66u firmware. Severity is critical (CVSS 9.8). Stack-based buffer overflow in Asuswrt-Merlin firmware for ASUS devices older than 384.4 and ASUS firmware before 3.0.0.4.382.50470 for devices allows remote attackers to execute arbitrary code by providing a long string to the blocking.asp

Q: How urgent is CVE-2018-8879?

Priority 69/100. Critical severity; EPSS top 3%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2018-8879 is a critical-severity flaw (CVSS 9.8) affecting rt-ac66u firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Stack-based buffer overflow in Asuswrt-Merlin firmware for ASUS devices older than 384.4 and ASUS firmware before 3.0.0.4.382.50470 for devices allows remote attackers to execute arbitrary code by providing a long string to the blocking.asp page via a GET or POST request. Vulnerable parameters are flag, mac, and cat_id.

Why this priority

Critical severity
EPSS top 3%: 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 score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	17.2% (top 3%)
CISA exploited list	No
Weakness	CWE-787
Published	2019-11-21
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: asus

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

Am I affected?

Timeline

2019-11-21 16:15 UTCPublished CVE record published
2026-06-17 02:05 UTCUpdated Record last modified

asus rt-ac66u firmware UPGRADE

Affected: < 3.0.0.4.382.50470

Fixed in: 3.0.0.4.382.50470

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-2018-8879?

rt-ac66u firmware: upgrade to 3.0.0.4.382.50470. Exact commands for each OS are on this page.

Is CVE-2018-8879 being exploited?

CVE-2018-8879 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-2018-8879 affect?

CVE-2018-8879 affects rt-ac66u firmware. Severity is critical (CVSS 9.8). Stack-based buffer overflow in Asuswrt-Merlin firmware for ASUS devices older than 384.4 and ASUS firmware before 3.0.0.4.382.50470 for devices allows remote attackers to execute arbitrary code by providing a long string to the blocking.asp

How urgent is CVE-2018-8879?

Priority 69/100. Critical severity; EPSS top 3%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2020-7997 MEDIUM 6.1 MITIGATE ASUS WRT-AC66U 3 RT 3.0.0.4.372_67 devices allow XSS via the Client Name field to the Parental Control feature
CVE-2018-9285 CRITICAL 9.8 UPGRADE UPGRADE Main_Analysis_Content.asp in /apply.cgi on ASUS RT-AC66U, RT-AC68U, RT-AC86U, RT-AC88U, RT-AC1900, RT-AC2900,
CVE-2018-8826 CRITICAL 9.8 MITIGATE MITIGATE ASUS RT-AC51U, RT-AC58U, RT-AC66U, RT-AC1750, RT-ACRH13, and RT-N12 D1 routers with firmware before 3.0.0.4.38
CVE-2017-11420 CRITICAL 9.8 UPGRADE UPGRADE Stack-based buffer overflow in ASUS_Discovery.c in networkmap in Asuswrt-Merlin firmware for ASUS devices and
CVE-2017-11345 HIGH 7.8 UPGRADE UPGRADE Stack buffer overflow in networkmap in Asuswrt-Merlin firmware for ASUS devices and ASUS firmware for ASUS RT-

References

← Back to latest CVEs