# CVE-2023-6906: Totolink A7100RU HTTP POST Request main buffer overflow

> Remote attackers can trigger a buffer overflow in the login handler of Totolink A7100RU routers, potentially leading to code execution.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 18 Dec 2023
- **Updated:** 7 May 2025

## What is CVE-2023-6906?

CVE-2023-6906 is a critical memory corruption vulnerability in Totolink A7100RU, published on 18 Dec 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability, which was classified as critical, was found in Totolink A7100RU 7.4cu.2313_B20191024. Affected is the function main of the file /cgi-bin/cstecgi.cgi?action=login of the component HTTP POST Request Handler. The manipulation of the argument flag with the input ie8 leads to buffer overflow. It is possible to launch the attack remotely. The exploit has been disclosed to the public and may be used. The identifier of this vulnerability is VDB-248268. NOTE: The vendor was contacted early about this disclosure but did not respond in any way.

Weakness: CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2023-6906?

It affects 1 product.


Products: Totolink A7100ru Firmware.

## How do I fix CVE-2023-6906?

No fix has been published for CVE-2023-6906 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-6906 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-6906 exists.

## Other vulnerabilities in Totolink A7100RU

- [CVE-2025-44655](https://insights.sbomify.com/CVE-2025-44655/): Path traversal in n/a (critical 9.8)
- [CVE-2023-7095](https://insights.sbomify.com/CVE-2023-7095/): Totolink A7100RU HTTP POST Request main buffer overflow (critical 9.8)
- [CVE-2023-33556](https://insights.sbomify.com/CVE-2023-33556/): Command injection in n/a (critical 9.8)
- [CVE-2023-30053](https://insights.sbomify.com/CVE-2023-30053/): Command injection in n/a (critical 9.8)
- [CVE-2023-30054](https://insights.sbomify.com/CVE-2023-30054/): Command injection in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-6906 and fix it if it is affected.

What it is: CVE-2023-6906 is a critical memory corruption vulnerability in Totolink A7100RU, published on 18 Dec 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-6906 exists.

Affected product: Totolink A7100RU. 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-2023-6906/ (Markdown: https://insights.sbomify.com/CVE-2023-6906/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-6906
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-6906
- OSV: https://osv.dev/vulnerability/CVE-2023-6906

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-6906/
Summaries are generated and may contain mistakes; the official description above is the record.