# CVE-2026-11771: Memory corruption in OpenVPN

> Attackers can cause a crash in OpenVPN clients via a crafted NTLM response from a malicious proxy server due to an off-by-one buffer write.

- **Severity:** High 7.0 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 30 Jul 2026
- **Updated:** 30 Jul 2026
- **Also known as:** ALPINE-CVE-2026-11771, DEBIAN-CVE-2026-11771, GHSA-v8ww-fhqp-9vff, UBUNTU-CVE-2026-11771

## What is CVE-2026-11771?

CVE-2026-11771 is a high-severity memory corruption vulnerability in OpenVPN, published on 30 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

OpenVPN version 2.1.0 through 2.6.20 and 2.7_alpha1 through 2.7.4 allows attackers via an off-by-one buffer write in the NTLM proxy authentication to potentially cause a crash via a crafted NTLM response from a malicious proxy server

Weakness: CWE-787 (Out-of-bounds Write), CWE-193 (Off-by-one Error), CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2026-11771?

It affects 1 product.


Products: Openvpn Openvpn.

## How do I fix CVE-2026-11771?

Upgrade to a fixed version.

## Is CVE-2026-11771 being exploited?

There is no known exploitation of CVE-2026-11771 in the wild and no public exploit code.

## Other vulnerabilities in OpenVPN

- [CVE-2025-12106](https://insights.sbomify.com/CVE-2025-12106/): Memory corruption in OpenVPN (critical 9.1)
- [CVE-2024-5594](https://insights.sbomify.com/CVE-2024-5594/): Information disclosure in OpenVPN (critical 9.1)
- [CVE-2018-7544](https://insights.sbomify.com/CVE-2018-7544/): Cross-site request forgery in n/a (critical 9.1)
- [CVE-2006-1629](https://insights.sbomify.com/CVE-2006-1629/): Code injection in n/a (critical 9.0)
- [CVE-2024-4877](https://insights.sbomify.com/CVE-2024-4877/): Privilege escalation in OpenVPN (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-11771 and fix it if it is affected.

What it is: CVE-2026-11771 is a high-severity memory corruption vulnerability in OpenVPN, published on 30 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-11771 in the wild and no public exploit code.

Affected product: OpenVPN. 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-2026-11771/ (Markdown: https://insights.sbomify.com/CVE-2026-11771/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-11771
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-11771
- OSV: https://osv.dev/vulnerability/CVE-2026-11771

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-11771/
Summaries are generated and may contain mistakes; the official description above is the record.