Hardcoded Telnet Backdoor in D-Link DIR-456U A1 Device
CVE-2026-42376

9.8CRITICAL

Key Information:

Vendor

D-link
Status
Dir-456u Firmware
Vendor
CVE Published:
4 May 2026

What is CVE-2026-42376?

The D-Link DIR-456U A1 device has a serious security flaw characterized by a hardcoded telnet backdoor. This backdoor allows an unauthenticated attacker on the local network to gain root access to the device. The device initializes a telnet daemon during boot, exposing a hardcoded username and password. This poses a significant risk, considering the device has reached End-of-Life status and will not receive any patches to mitigate this vulnerability.

Affected Version(s)

DIR-456U Firmware MIPS32 Little-Endian A1

References

https://www.securin.io/zero-day/cve-2026-42376-hardcoded-...

CVSS V3.1

Score:
9.8
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Arjun Basnet from Securin Labs
.