CVE-2026-5211
Remote Stack-Based Buffer Overflow in D-Link UPnP Server
Publication date: 2026-03-31
Last updated on: 2026-04-02
Assigner: VulDB
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| dlink | dnr-202l_firmware | to 2026-02-05 (inc) |
| dlink | dnr-326_firmware | to 2026-02-05 (inc) |
| dlink | dns-1100-4_firmware | to 2026-02-05 (inc) |
| dlink | dns-120_firmware | to 2026-02-05 (inc) |
| dlink | dns-1200-05_firmware | to 2026-02-05 (inc) |
| dlink | dns-1550-04_firmware | to 2026-02-05 (inc) |
| dlink | dns-315l_firmware | to 2026-02-05 (inc) |
| dlink | dns-320_firmware | to 2026-02-05 (inc) |
| dlink | dns-320l_firmware | to 2026-02-05 (inc) |
| dlink | dns-320lw_firmware | to 2026-02-05 (inc) |
| dlink | dns-321_firmware | to 2026-02-05 (inc) |
| dlink | dns-322l_firmware | to 2026-02-05 (inc) |
| dlink | dns-323_firmware | to 2026-02-05 (inc) |
| dlink | dns-325_firmware | to 2026-02-05 (inc) |
| dlink | dns-326_firmware | to 2026-02-05 (inc) |
| dlink | dns-327l_firmware | to 2026-02-05 (inc) |
| dlink | dns-340l_firmware | to 2026-02-05 (inc) |
| dlink | dns-343_firmware | to 2026-02-05 (inc) |
| dlink | dns-345_firmware | to 2026-02-05 (inc) |
| dlink | dns-726-4_firmware | to 2026-02-05 (inc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-119 | The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data. |
| CWE-787 | The product writes data past the end, or before the beginning, of the intended buffer. |
| CWE-121 | A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). |
Attack-Flow Graph
AI Powered Q&A
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.
Can you explain this vulnerability to me?
CVE-2026-5211 is a stack-based buffer overflow vulnerability found in certain D-Link NAS devices. It exists in the UPnP_AV_Server_Path_Del function within the /cgi-bin/app_mgr.cgi file. The vulnerability occurs because the function improperly handles the input parameter 'f_dir', which is supplied by an attacker. When an excessively long 'f_dir' value is sent, it overflows the stack buffer and overwrites the function's return address.
This flaw allows remote attackers to crash the device by sending a specially crafted POST request, potentially leading to denial of service or even arbitrary code execution.
How can this vulnerability impact me? :
This vulnerability can have serious impacts including causing the affected D-Link device to crash and become unresponsive, resulting in a denial of service. Because the buffer overflow can overwrite the return address, it may also allow remote attackers to execute arbitrary code on the device.
Such impacts can disrupt network services relying on the device, potentially leading to downtime and loss of availability.
How can this vulnerability be detected on my network or system? Can you suggest some commands?
This vulnerability can be detected by sending a specially crafted POST request to the affected device's /cgi-bin/app_mgr.cgi endpoint, targeting the UPnP_AV_Server_Path_Del function with an excessively long f_dir parameter.
A proof of concept involves sending a POST request with the parameter cmd=UPnP_AV_Server_Path_Del and a very long string of repeated characters (e.g., 'a') as the value of f_dir. If the device crashes or becomes unresponsive, it indicates the presence of the vulnerability.
- Example curl command to test the vulnerability:
- curl -X POST http://<target-ip>/cgi-bin/app_mgr.cgi -d "cmd=UPnP_AV_Server_Path_Del&f_dir=$(python3 -c 'print("a"*1000)')"
Monitoring for crashes or unresponsiveness after sending such requests can help detect the vulnerability on your network or system.
What immediate steps should I take to mitigate this vulnerability?
Immediate mitigation steps include restricting access to the vulnerable device's management interface to trusted networks only, such as internal networks or VPNs.
Avoid exposing the /cgi-bin/app_mgr.cgi endpoint to untrusted or public networks to prevent remote exploitation.
If possible, apply any available firmware updates or patches provided by the vendor that address this vulnerability.
As a temporary measure, consider disabling UPnP services or the affected CGI functionality if the device configuration allows.
Monitor device logs and network traffic for suspicious POST requests targeting /cgi-bin/app_mgr.cgi with unusual parameters.