Executive Summary
A second critical stack-based buffer overflow has been disclosed in the D-Link DIR-825M router, firmware version 1.1.8, this time in the LTE module firmware-upgrade handler. CVE-2026-82593 affects sub_41802C, the function behind the /boafrm/formLtefotaUpgradeFibocom endpoint. Because the fota_url argument is copied onto the stack without a bounds check, a remote, unauthenticated attacker can overflow adjacent memory and potentially achieve arbitrary code execution. It carries a CVSS score of 9.9 (Critical), and a public exploit has already been published.
Vulnerability Overview
| Attribute | Value |
|---|---|
| CVE ID | CVE-2026-82593 |
| CVSS Score | 9.4–9.9 (Critical) |
| Type | Stack-Based Buffer Overflow (CWE-121) |
| Component | sub_41802C in /boafrm/formLtefotaUpgradeFibocom (LTE Module Firmware Upgrade) |
| Attack Vector | Network (remote, unauthenticated) |
| Privileges Required | None |
| User Interaction | None |
| Exploit Status | Public exploit available |
Technical Details
The /boafrm/formLtefotaUpgradeFibocom endpoint handles firmware-over-the-air (FOTA) upgrade requests for the router's Fibocom LTE module, letting the router pull an update from a specified URL. The handler function, sub_41802C, copies the fota_url parameter into a fixed-size stack buffer without validating its length.
1. Attacker sends a crafted request to /boafrm/formLtefotaUpgradeFibocom
2. The "fota_url" argument contains data exceeding the allocated buffer size
3. sub_41802C copies the oversized value onto the stack without bounds checking
4. Adjacent stack memory — including saved return addresses — is overwritten
5. Attacker-controlled data can redirect execution, enabling remote code executionAs with the related disk-formatting overflow, CVE-2026-82592, disclosed the same week, no authentication or user interaction is required — any attacker able to reach the router's web management interface can trigger the overflow. Consumer routers with remote/WAN management enabled are exploitable directly from the internet.
Impact
| Impact | Description |
|---|---|
| Remote Code Execution | Attacker-controlled stack overwrite can redirect execution flow |
| Full Device Compromise | Successful exploitation can grant control of the router's firmware environment |
| Malicious Firmware Delivery | The affected endpoint already controls firmware-update URLs, raising the risk of chaining with a rogue update source |
| No Authentication Required | Fully exploitable by an anonymous, unauthenticated attacker |
Remediation
No vendor patch has been referenced in public advisories for this CVE as of this writing. Given the availability of a public exploit, treat this as actively exploitable and apply the following mitigations immediately:
- Disable remote/WAN-side management on the DIR-825M so the web administration interface is only reachable from the trusted LAN.
- Check D-Link's support pages for firmware updates specific to the DIR-825M and apply any available patch.
- Replace end-of-life hardware — the DIR-825M is a legacy model; if D-Link does not ship a fix, plan migration to a currently supported router.
- Segment IoT and router management traffic from sensitive internal networks using VLANs, limiting the blast radius of a compromised router.
- Monitor for anomalous requests to
/boafrm/formLtefotaUpgradeFibocomand otherboafrmendpoints in router logs, where logging is available.
Detection
| Indicator | Description |
|---|---|
Requests to /boafrm/formLtefotaUpgradeFibocom with abnormally long fota_url values | Signature of exploitation attempts |
| Unexpected router reboots, crash loops, or firmware-update prompts | Possible sign of failed or repeated exploitation attempts |
| Unrecognized outbound connections from the router itself | Possible sign of a compromised device |