CVE-2026-42376— D-Link DIR-456U A1 Hardcoded Telnet Backdoor Credentials
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I. Basic Information for CVE-2026-42376
Vulnerability Information
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Vulnerability Title
D-Link DIR-456U A1 Hardcoded Telnet Backdoor Credentials
Source: NVD (National Vulnerability Database)
Vulnerability 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.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
使用硬编码的凭证
Source: NVD (National Vulnerability Database)
Vulnerability Title
D-Link DIR-456U 信任管理问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
D-Link DIR-456U是中国友讯（D-Link）公司的一款无线路由器。 D-Link DIR-456U Hardware Revision A1存在信任管理问题漏洞，该漏洞源于硬编码的telnet后门，可能导致本地网络上的未认证攻击者获得root shell并完全控制设备。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
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Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| D-Link | DIR-456U Firmware | A1 | cpe:2.3:o:dlink:dir-456u_firmware:*:*:*:*:*:*:*:* |
II. Public POCs for CVE-2026-42376
| # | POC Description | Source Link | Shenlong Link |
|---|
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Same Patch Batch · D-Link · 2026-05-04 · 5 CVEs total
| CVE-2026-42375 | 9.8 CRITICAL | D-Link DIR-600L A1 Hardcoded Telnet Backdoor Credentials |
| CVE-2026-42374 | 9.8 CRITICAL | D-Link DIR-600L B1 Hardcoded Telnet Backdoor Credentials |
| CVE-2026-42373 | 9.8 CRITICAL | D-Link DIR-605L B2 Hardcoded Telnet Backdoor Credentials |
| CVE-2026-42372 | 8.8 HIGH | D-Link DIR-605L A1 Hardcoded Telnet Backdoor Credentials |
IV. Related Vulnerabilities
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V. Comments for CVE-2026-42376
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