# CVE-2026-125406: Ettercap through 0.8.4.1 Stack Buffer Underwrite via Telnet Dissector Backspace Handling


- **Severity:** High 8.7 (`CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 9 Nov 2026
- **Updated:** 9 Nov 2026
- **Also known as:** DEBIAN-CVE-2026-125406, GHSA-cq94-w9q3-ggxw, GHSA-w5ch-7c4x-crcc, UBUNTU-CVE-2026-125406

## What is CVE-2026-125406?

CVE-2026-125406 is a high-severity vulnerability in ettercap, published on 9 Nov 2026. 

### Official description

Ettercap through 0.8.4.1 contains a stack buffer underwrite vulnerability in the telnet dissector in src/dissectors/ec_telnet.c that decrements the output pointer on backspace without a lower bound check. Attackers can send a telnet stream with more backspaces than preceding characters to write below the stack buffer, corrupting the stack of the Ettercap process that normally runs as root.

Weakness: CWE-124 (Buffer Underwrite)

## Which versions are affected by CVE-2026-125406?


## How do I fix CVE-2026-125406?

No fix has been published for CVE-2026-125406 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-125406 being exploited?

There is no known exploitation of CVE-2026-125406 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-125406 and fix it if it is affected.

What it is: CVE-2026-125406 is a high-severity vulnerability in ettercap, published on 9 Nov 2026. 
Exploitation: There is no known exploitation of CVE-2026-125406 in the wild and no public exploit code.

Affected product: ettercap. 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-2026-125406/ (Markdown: https://insights.sbomify.com/CVE-2026-125406/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-125406
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-125406
- OSV: https://osv.dev/vulnerability/CVE-2026-125406

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-125406/
Summaries are generated and may contain mistakes; the official description above is the record.