# CVE-2016-20047: EKG Gadu 1.9 Local Buffer Overflow via Username Parameter

> Local attackers can execute arbitrary code by supplying an oversized username string to trigger a buffer overflow in EKG Gadu.

- **Severity:** High 8.6 (`CVSS:4.0/AV:L/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
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 28 Mar 2026
- **Updated:** 30 Mar 2026
- **Also known as:** GHSA-v8g9-6wqg-f384

## What is CVE-2016-20047?

CVE-2016-20047 is a high-severity memory corruption vulnerability in EKG Gadu, published on 28 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

EKG Gadu 1.9~pre+r2855-3+b1 contains a local buffer overflow vulnerability in the username handling that allows local attackers to execute arbitrary code by supplying an oversized username string. Attackers can trigger the overflow in the strlcpy function by passing a crafted buffer exceeding 258 bytes to overwrite the instruction pointer and execute shellcode with user privileges.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2016-20047?


## How do I fix CVE-2016-20047?

No fix has been published for CVE-2016-20047 yet. Limit exposure of the affected software until one is available.

## Is CVE-2016-20047 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2016-20047 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-20047 and fix it if it is affected.

What it is: CVE-2016-20047 is a high-severity memory corruption vulnerability in EKG Gadu, published on 28 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2016-20047 exists.

Affected product: EKG Gadu. 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-2016-20047/ (Markdown: https://insights.sbomify.com/CVE-2016-20047/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-20047
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-20047
- OSV: https://osv.dev/vulnerability/CVE-2016-20047

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From sbomify Insights: https://insights.sbomify.com/CVE-2016-20047/
Summaries are generated and may contain mistakes; the official description above is the record.