# CVE-2026-123957: TOTOLINK CA300-PoE cstecgi.cgi setIpQosRules buffer overflow


- **Severity:** Critical 9.4 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:P`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 7 Nov 2026
- **Updated:** 9 Nov 2026
- **Also known as:** GHSA-wxh7-x4wq-j3rp

## What is CVE-2026-123957?

CVE-2026-123957 is a critical vulnerability in TOTOLINK CA300-PoE, published on 7 Nov 2026. 

### Official description

A vulnerability was determined in TOTOLINK CA300-PoE 6.2c.884. Impacted is the function setIpQosRules of the file /cgi-bin/cstecgi.cgi. This manipulation of the argument ipStart causes buffer overflow. It is possible to initiate the attack remotely. The exploit has been publicly disclosed and may be utilized.

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-2026-123957?


## How do I fix CVE-2026-123957?

No fix has been published for CVE-2026-123957 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-123957 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-123957 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-123957 and fix it if it is affected.

What it is: CVE-2026-123957 is a critical vulnerability in TOTOLINK CA300-PoE, published on 7 Nov 2026. 
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-123957 exists.

Affected product: TOTOLINK CA300-PoE. 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-2026-123957/ (Markdown: https://insights.sbomify.com/CVE-2026-123957/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-123957
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-123957
- OSV: https://osv.dev/vulnerability/CVE-2026-123957

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-123957/
Summaries are generated and may contain mistakes; the official description above is the record.