# CVE-2026-7749: Totolink N300RH POST Request cstecgi.cgi setWanConfig buffer overflow

> Remote attackers can trigger a buffer overflow in the Totolink N300RH router's WAN configuration handler, potentially leading to arbitrary code execution.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 4 May 2026
- **Updated:** 5 May 2026
- **Also known as:** GHSA-9639-rx99-qmgv

## What is CVE-2026-7749?

CVE-2026-7749 is a high-severity memory corruption vulnerability in Totolink N300RH, published on 4 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A security vulnerability has been detected in Totolink N300RH 3.2.4-B20220812. This affects the function setWanConfig of the file /cgi-bin/cstecgi.cgi of the component POST Request Handler. The manipulation of the argument priDns leads to buffer overflow. The attack may be initiated remotely. The exploit has been disclosed publicly and may be used.

Weakness: CWE-120 (Buffer Copy without Checking Size of Input), CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2026-7749?


## How do I fix CVE-2026-7749?

No fix has been published for CVE-2026-7749 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-7749 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-7749 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-7749 and fix it if it is affected.

What it is: CVE-2026-7749 is a high-severity memory corruption vulnerability in Totolink N300RH, published on 4 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-7749 exists.

Affected product: Totolink N300RH. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-7749/ (Markdown: https://insights.sbomify.com/CVE-2026-7749/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-7749
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-7749
- OSV: https://osv.dev/vulnerability/CVE-2026-7749

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-7749/
Summaries are generated and may contain mistakes; the official description above is the record.