CVE-2021-46381

What it actually does

This is an unauthenticated network-reachable path traversal/local file inclusion flaw in the D-Link DAP-1620 firmware web interface. By placing directory traversal sequences in a vulnerable file path parameter, an attacker can cause the device to read files outside the intended web directory. The described impact includes disclosure of sensitive local files such as /etc/passwd and /etc/shadow, which can expose local account metadata and password hashes. The flaw primarily affects confidentiality; it does not directly provide code execution, data modification, or denial of service, but disclosed credentials may enable follow-on compromise.

Why it matters to the business

An exposed vulnerable D-Link DAP-1620 range extender can leak sensitive system files to anyone who can reach its management interface. If password hashes or configuration secrets are recovered and cracked, attackers may gain administrative access to the device, change network settings, monitor or disrupt connectivity, or use the device as a foothold inside the network. The issue is not listed in CISA KEV, but the exploit is described as weaponized and has a relatively high EPSS score, so internet- or guest-network-exposed devices should be treated as urgent risk even though no fixed version was provided in the input.

How an attack unfolds

An attacker first discovers a D-Link DAP-1620 management interface reachable over the network, commonly through internet scanning, local wireless access, or access to a routed internal segment. The attacker sends a crafted HTTP request to the vulnerable web interface that includes path traversal sequences such as ../ in a file path or resource parameter. Instead of constraining the request to the intended directory, the firmware resolves the traversal and returns the contents of internal files. The attacker typically targets /etc/passwd to confirm the vulnerability and /etc/shadow to obtain password hashes. Those hashes can then be cracked offline or combined with other exposed configuration data to attempt administrative login, persistence through configuration changes, or further movement into the surrounding network.

How to fix it

Upgrade the D-Link DAP-1620 firmware to a vendor-provided fixed release if one is available from D-Link support or the official firmware download portal. Because no fixed version was provided, organizations should verify the latest firmware directly with the vendor and consider replacing or retiring devices that cannot be updated. Until patched or replaced, disable remote administration, restrict the management interface to a dedicated trusted management network, block access from the internet and guest Wi-Fi, enforce strong unique administrator credentials, and monitor for traversal attempts. If exploitation is suspected, reset the device to factory defaults, install known-good firmware, rotate device administrator passwords and any reused credentials, and review network configuration for unauthorized changes.

How to confirm the fix worked

Inventory D-Link DAP-1620 devices and record firmware versions, management exposure, and whether remote administration is enabled. Confirm whether the installed firmware is the latest available from D-Link. From an authorized test network, validate that traversal payloads are rejected and do not return local file contents; a vulnerable response may include recognizable /etc/passwd content such as root: or other system account entries. Prefer using a vulnerability scanner or a controlled proof-of-concept in a lab or maintenance window. Also verify that firewall, ACL, and Wi-Fi segmentation rules prevent untrusted networks from reaching the management interface.

Typical attack path

1. Identify a reachable D-Link DAP-1620 web management interface.
2. Fingerprint the device or firmware through banners, login pages, static assets, or network scan results.
3. Send crafted HTTP requests containing path traversal sequences to a vulnerable file/resource parameter.
4. Confirm exposure by retrieving a known local file such as /etc/passwd.
5. Attempt to retrieve more sensitive files such as /etc/shadow or configuration files.
6. Crack disclosed password hashes or reuse recovered credentials against the device management interface.
7. Use administrative access to alter device settings, maintain access, intercept traffic, or pivot to adjacent network resources.

How to detect it

Review HTTP access logs from the DAP-1620 management interface if available, upstream reverse proxies, firewall logs, IDS/IPS alerts, and packet captures for requests containing directory traversal sequences or attempts to access Linux system files. Focus on unauthenticated GET or POST requests to management endpoints with parameters or paths containing ../, URL-encoded traversal variants, or target filenames such as /etc/passwd and /etc/shadow. Correlate suspicious requests with subsequent successful logins, configuration changes, firmware upload events, DNS or gateway changes, new remote administration exposure, unexpected reboots, or administrator password changes. Because embedded devices may retain limited logs, network telemetry and perimeter logs are often the best historical sources. If /etc/shadow may have been accessed, treat local device credentials as exposed and investigate whether the same credentials were reused elsewhere.

• ../etc/passwd
• ../../etc/passwd
• ../../../etc/passwd
• ../../../../etc/passwd
• ../../../../../etc/passwd
• ../../../../../../etc/passwd
• /etc/passwd
• ../etc/shadow
• ../../etc/shadow
• ../../../etc/shadow
• ../../../../etc/shadow
• ../../../../../etc/shadow
• ../../../../../../etc/shadow
• /etc/shadow
• ..%2f..%2fetc%2fpasswd
• ..%2F..%2Fetc%2Fpasswd
• %2e%2e%2f%2e%2e%2fetc%2fpasswd
• ..%2f..%2fetc%2fshadow
• ..%2F..%2Fetc%2Fshadow
• %2e%2e%2f%2e%2e%2fetc%2fshadow
• ..%252f..%252fetc%252fpasswd
• ..%252f..%252fetc%252fshadow
• root:x:0:0:
• root:$

What your security team should do

• Immediately identify D-Link DAP-1620 devices and determine whether their management interfaces are reachable from the internet, guest Wi-Fi, or untrusted internal segments.
• Upgrade to the latest vendor firmware where available; replace or decommission devices with no available fix or unsupported firmware.
• Disable remote administration and restrict management access to trusted administrator IP ranges or a dedicated management VLAN.
• Search historical web, firewall, IDS/IPS, and reverse proxy logs for path traversal attempts targeting the device management interface.
• If suspicious file disclosure is found, rotate device administrator credentials, review configuration for unauthorized changes, and consider factory reset plus clean firmware installation.
• Add IDS/SIEM detections for HTTP requests containing traversal sequences and sensitive Linux file targets such as /etc/passwd and /etc/shadow.
• Prioritize remediation because exploit maturity is weaponized and EPSS indicates meaningful likelihood of exploitation despite the CVE not being listed in CISA KEV.