CVE-2025-13549 Overview
CVE-2025-13549 is a buffer overflow vulnerability affecting D-Link DIR-822K routers running firmware version 1.00. The flaw resides in the sub_455524 function within the /boafrm/formNtp endpoint of the embedded web server. Attackers can trigger the overflow by manipulating the submit-url argument in HTTP requests. The vulnerability is remotely exploitable over the network and a public exploit has been disclosed, increasing the risk of opportunistic attacks against exposed devices. The weakness is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer).
Critical Impact
Remote attackers with low-privileged access can corrupt memory on D-Link DIR-822K devices through crafted HTTP requests, potentially leading to arbitrary code execution or denial of service on the router.
Affected Products
- D-Link DIR-822K firmware version 1.00 (build 20250513164613)
- D-Link DIR-822K hardware router
- Network deployments exposing the device web management interface
Discovery Timeline
- 2025-11-23 - CVE-2025-13549 published to NVD
- 2025-12-02 - Last updated in NVD database
Technical Details for CVE-2025-13549
Vulnerability Analysis
The vulnerability resides in sub_455524, a handler function reached through the /boafrm/formNtp URI of the Boa web server embedded in DIR-822K firmware. This endpoint processes Network Time Protocol (NTP) configuration submissions from the router administrative interface. When the function processes the submit-url parameter from incoming HTTP POST requests, it copies attacker-controlled data into a fixed-size stack or heap buffer without enforcing length boundaries. Sending an oversized submit-url value overruns the destination buffer and overwrites adjacent memory, including saved return addresses and control structures.
Remote attackers with authenticated access to the management interface can deliver the payload over the network. Successful exploitation impacts confidentiality, integrity, and availability on the affected device. A public proof-of-concept is referenced through the GitHub CVE Issue Discussion and VulDB #333316.
Root Cause
The root cause is missing input validation and unsafe memory copy operations on the submit-url request parameter. The function does not verify the length of the user-supplied string before writing it into a fixed-size buffer, satisfying the conditions of [CWE-119].
Attack Vector
An attacker sends a crafted HTTP request to /boafrm/formNtp containing an oversized submit-url argument. Because the attack is delivered over the network with low complexity, any reachable instance of the management interface, including those exposed through misconfiguration or weak segmentation, is at risk. The vulnerability mechanism is documented in the public references; no synthetic exploit code is reproduced here.
Detection Methods for CVE-2025-13549
Indicators of Compromise
- HTTP POST requests to /boafrm/formNtp containing unusually long submit-url parameter values exceeding typical URL lengths.
- Unexpected reboots, web server crashes, or process restarts on DIR-822K devices following inbound requests to the NTP configuration endpoint.
- Outbound connections from the router to unfamiliar hosts after suspicious administrative requests, indicating possible post-exploitation activity.
Detection Strategies
- Inspect web server access logs on the router for repeated requests to /boafrm/formNtp from unauthorized source IPs.
- Deploy network-based intrusion detection signatures that flag HTTP request bodies with submit-url field lengths beyond reasonable thresholds.
- Correlate authentication events with subsequent administrative POSTs to identify brute-force followed by exploitation patterns.
Monitoring Recommendations
- Monitor management plane traffic to and from DIR-822K devices and alert on access from non-administrative network segments.
- Capture and review router syslog output for crash signatures, segmentation faults, or watchdog-induced reboots.
- Track firmware build identifiers in inventory systems to detect devices running the vulnerable 1.00 release.
How to Mitigate CVE-2025-13549
Immediate Actions Required
- Restrict access to the DIR-822K web management interface to trusted internal administrative subnets only, and disable WAN-side management.
- Rotate administrative credentials and enforce strong, unique passwords to reduce the risk of low-privileged attackers gaining the access needed to trigger the flaw.
- Audit network exposure of all DIR-822K devices and remove any direct internet-facing management endpoints.
Patch Information
At the time of publication, no vendor advisory or fixed firmware release for CVE-2025-13549 is listed in the available references. Administrators should monitor D-Link Security Resources for an updated firmware release addressing the sub_455524 handler in /boafrm/formNtp. Additional technical detail is tracked at VulDB CTI ID #333316.
Workarounds
- Disable remote (WAN) administration on the router and require management access only through a wired LAN connection.
- Place vulnerable devices behind a network firewall that filters HTTP traffic to /boafrm/formNtp from untrusted sources.
- Consider replacing end-of-support or unpatched DIR-822K hardware with a currently supported router model if no fix becomes available.
# Example firewall rule restricting access to the router admin interface
# Replace 192.0.2.0/24 with your trusted management subnet
iptables -A INPUT -p tcp --dport 80 -s 192.0.2.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 192.0.2.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
