# CVE-2019-3855: Integer overflow in libssh2

> A remote attacker can execute code on a client system via an integer overflow in libssh2 when connecting to a compromised SSH server.

- **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:** 21 Mar 2019
- **Updated:** 14 Oct 2026
- **Also known as:** ALPINE-CVE-2019-3855, DEBIAN-CVE-2019-3855, GHSA-hhcg-w86v-64g8, UBUNTU-CVE-2019-3855

## What is CVE-2019-3855?

CVE-2019-3855 is a high-severity vulnerability in Apple Xcode, published on 21 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

An integer overflow flaw which could lead to an out of bounds write was discovered in libssh2 before 1.8.1 in the way packets are read from the server. A remote attacker who compromises a SSH server may be able to execute code on the client system when a user connects to the server.

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

## Which versions are affected by CVE-2019-3855?

It affects 14 products.


Products: Apple Xcode, Debian Debian Linux, Fedoraproject Fedora, Libssh2 Libssh2, Netapp Ontap Select Deploy Administration Utility, Opensuse Leap, Oracle Peoplesoft Enterprise Peopletools, Redhat Enterprise Linux, 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-2019-3855?

Upgrade to a fixed version.

## Is CVE-2019-3855 being exploited?

There is no known exploitation of CVE-2019-3855 in the wild and no public exploit code.

## Other vulnerabilities in Apple Xcode

- [CVE-2025-48384](https://insights.sbomify.com/CVE-2025-48384/): Git Link Following (high 8.1, exploited in the wild)
- [CVE-2014-9390](https://insights.sbomify.com/CVE-2014-9390/): JGit Improper Input Validation vulnerability (critical 9.8)
- [CVE-2019-14379](https://insights.sbomify.com/CVE-2019-14379/): Deserialization of untrusted data in FasterXML jackson-databind (critical 9.8)
- [CVE-2018-4164](https://insights.sbomify.com/CVE-2018-4164/): An issue was discovered in certain Apple products. (critical 9.8)
- [CVE-2016-0746](https://insights.sbomify.com/CVE-2016-0746/): Use after free in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-3855 and fix it if it is affected.

What it is: CVE-2019-3855 is a high-severity vulnerability in Apple Xcode, published on 21 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-2019-3855 in the wild and no public exploit code.

Affected product: Apple Xcode. 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-2019-3855/ (Markdown: https://insights.sbomify.com/CVE-2019-3855/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-3855
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-3855
- OSV: https://osv.dev/vulnerability/CVE-2019-3855

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-3855/
Summaries are generated and may contain mistakes; the official description above is the record.