# CVE-2026-109438: 3proxy 0.9.7 - 1.0.1 Uninitialized Stack Memory Disclosure via SOCKS4

> Unauthenticated attackers can leak stack memory via SOCKS4 replies when external-NAT is enabled, weakening ASLR protections in 3proxy.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Oct 2026
- **Updated:** 27 Oct 2026
- **Also known as:** GHSA-4226-q7gw-49h8

## What is CVE-2026-109438?

CVE-2026-109438 is a medium-severity vulnerability in 3proxy, published on 14 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

3proxy from 0.9.7 through 1.0.1, fixed in commit 206c923, contains an uninitialized stack memory disclosure vulnerability that allows unauthenticated attackers to leak stack bytes via the SOCKS4 reply path when the external-NAT option (-Ne) is configured. Attackers can send a client probe that fails the SOCKS version check to trigger a reply containing uninitialized bytes from the sin structure, exposing high bytes of a userspace pointer that weakens ASLR protections.

Weakness: CWE-908 (Use of Uninitialized Resource)

## Which versions are affected by CVE-2026-109438?


## How do I fix CVE-2026-109438?

No fix has been published for CVE-2026-109438 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-109438 being exploited?

There is no known exploitation of CVE-2026-109438 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-109438 and fix it if it is affected.

What it is: CVE-2026-109438 is a medium-severity vulnerability in 3proxy, published on 14 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-109438 in the wild and no public exploit code.

Affected product: 3proxy. 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-2026-109438/ (Markdown: https://insights.sbomify.com/CVE-2026-109438/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-109438
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-109438
- OSV: https://osv.dev/vulnerability/CVE-2026-109438

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-109438/
Summaries are generated and may contain mistakes; the official description above is the record.