CVE-2019-3856 Integer overflow in libssh2

What is CVE-2019-3856?

CVE-2019-3856 is a high-severity 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

An integer overflow flaw, which could lead to an out of bounds write, was discovered in libssh2 before 1.8.1 in the way keyboard prompt requests are parsed. 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, CWE-190

Which versions are affected by CVE-2019-3856?

It affects 13 products.

Products include Debian Debian Linux, Fedoraproject Fedora, Libssh2 Libssh2, Netapp Ontap Select Deploy Administration Utility, Opensuse Leap, Oracle Peoplesoft Enterprise Peopletools and 7 more.

How do I fix CVE-2019-3856?

Upgrade to a fixed version.

Is CVE-2019-3856 being exploited?

There is no known exploitation of CVE-2019-3856 in the wild and no public exploit code.

Other vulnerabilities in Debian Debian Linux

• CVE-2015-3306 ProFTPD Improper Access Control Exploited Critical 10.0
• CVE-2025-49113 RoundCube Webmail Deserialization of Untrusted Data Exploited Critical 9.9
• CVE-2026-24061 GNU InetUtils Argument Injection Exploited Critical 9.8
• CVE-2025-39682 Linux Kernel Improper Check for Unusual or Exceptional Conditions Exploited Critical 9.8
• CVE-2024-9680 Mozilla Firefox Use-After-Free Exploited Critical 9.8

All Debian Debian Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ALPINE-CVE-2019-3856, DEBIAN-CVE-2019-3856, GHSA-w4mw-p8mf-732j, UBUNTU-CVE-2019-3856.