# CVE-2019-3863: Memory corruption in libssh2

> A malicious SSH server can trigger an out-of-bounds memory write in libssh2 clients, potentially leading to code execution or crashes.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A: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:** 25 Mar 2019
- **Updated:** 14 Oct 2026
- **Also known as:** ALPINE-CVE-2019-3863, DEBIAN-CVE-2019-3863, GHSA-h63q-2463-x5hq, UBUNTU-CVE-2019-3863

## What is CVE-2019-3863?

CVE-2019-3863 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 25 Mar 2019. 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

A flaw was found in libssh2 before 1.8.1 creating a vulnerability on the SSH client side. A server could send a multiple keyboard interactive response messages whose total length are greater than unsigned char max characters. This value is used by the SSH client as an index to copy memory causing in an out of bounds memory write error.

Weakness: CWE-787 (Out-of-bounds Write), CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2019-3863?

It affects 10 products.


Products: Debian Debian Linux, Libssh2 Libssh2, Netapp Ontap Select Deploy Administration Utility, Opensuse Leap, Redhat Enterprise Linux Desktop, Redhat Enterprise Linux Server, Redhat Enterprise Linux Server Aus, Redhat Enterprise Linux Server Eus, Redhat Enterprise Linux Server Tus, Redhat Enterprise Linux Workstation.

## How do I fix CVE-2019-3863?

Upgrade to a fixed version.

## Is CVE-2019-3863 being exploited?

There is no known exploitation of CVE-2019-3863 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-3863 and fix it if it is affected.

What it is: CVE-2019-3863 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 25 Mar 2019. 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-2019-3863 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2019-3863/ (Markdown: https://insights.sbomify.com/CVE-2019-3863/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-3863
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-3863
- OSV: https://osv.dev/vulnerability/CVE-2019-3863

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-3863/
Summaries are generated and may contain mistakes; the official description above is the record.