CVE-2024-40891: Zyxel DSL CPE OS Command Injection Vulnerability

What CISA requires

The impacted product could be end-of-life (EoL) and/or end-of-service (EoS). Users should discontinue product utilization if a current mitigation is unavailable.

Forensic triage

No

What to do now

1. Find every instance of DSL CPE Devices you run, including the forgotten ones, and check its version against the vendor advisory.
2. Apply the vendor's fix or mitigation, before March 4, 2025 if you are bound by CISA's deadline, sooner if it faces the internet.
3. Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.
4. Until every instance is patched, block the attack at the edge: a WAF in blocking mode stops OS command injection payloads, including Shellshock.

References

• https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-command-injection-and-insecure-default-credentials-vulnerabilities-in-certain-legacy-dsl-cpe-02-04-2025
• https://www.zyxel.com/service-provider/global/en/security-advisories/zyxel-security-advisory-command-injection-insecure-in-certain-legacy-dsl-cpe-02-04-2025
• https://nvd.nist.gov/vuln/detail/CVE-2024-40891

CVE-2024-40891 in the National Vulnerability Database