Threats / Zyxel / CVE-2024-40891
CVE-2024-40891
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Zyxel DSL CPE Devices vulnerability
Zyxel DSL CPE devices contain a post-authentication command injection vulnerability allowing authenticated attackers to execute arbitrary OS commands via Telnet.
Verdict
Today item — known-exploited.
An authenticated attacker can inject OS commands through management interfaces on vulnerable Zyxel DSL CPE devices, achieving arbitrary code execution. The vulnerability is actively exploited in the wild.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
3 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2025-02-11).
Probability (EPSS)
EPSS 0.2048 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Zyxel, DSL CPE Devices. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-78 OS Command Injection — weakness family: Injection.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I gain valid credentials for the device management interface through phishing, credential stuffing, or default credentials.
Business
Attackers with legitimate access pathways can bypass initial authentication barriers, increasing the attack surface for internal network compromise.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I connect via Telnet and inject shell metacharacters into management commands to execute arbitrary OS-level operations.
Business
The device becomes a foothold for lateral movement, data exfiltration, or deployment of persistent malware within the network.
3
Lateral reach — past segmentation narrative 3
Attacker
I establish persistent access or pivot to other network segments using the compromised CPE as a trusted internal node.
Business
Critical infrastructure and customer networks face operational disruption, data loss, and extended recovery costs from widespread device compromise.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05