CVE-2026-42376 D-Link DIR-456U A1 Hardcoded Telnet Backdoor Credentials
Attackers on the local network can use hardcoded credentials to gain root access to the EOL D-Link DIR-456U router.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-42376?
CVE-2026-42376 is a critical vulnerability in D-Link DIR-456U Firmware, published on 4 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
D-Link DIR-456U Hardware Revision A1 (End-of-Life, EOL) contains a hardcoded telnet backdoor. The device starts a telnet daemon at boot via /etc/init0.d/S80telnetd.sh with the username "Alphanetworks" and the static password "whdrv01_dlob_dir456U" read from /etc/config/image_sign. The custom telnetd binary accepts a -u user:password flag, and the custom login binary uses strcmp() to validate credentials. Successful authentication grants an unauthenticated attacker on the local network a root shell with full administrative control. The device has reached End-of-Life (EOL) and will not receive patches.
Weakness: CWE-798
Which versions are affected by CVE-2026-42376?
It affects 1 product.
Products include Dlink Dir-456u Firmware.
How do I fix CVE-2026-42376?
No fix has been published for CVE-2026-42376 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-42376 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42376 exists.
Sources
Also known as GHSA-8fmw-7p6g-ww4q.