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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-authenti...

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.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This OpenSSH issue affects only unusual builds using the experimental XMSS key type. In that narrow configuration, malformed XMSS key handling can corrupt memory before authentication. Most standard OpenSSH deployments are unlikely to be exposed, but vendors may have shipped affected packages or products.

Executive priority

Treat as a targeted verification item, not an emergency for typical OpenSSH estates. The impact is serious where XMSS is enabled, but the required experimental configuration makes broad exposure less likely.

Technical view

CVE-2019-16905 is an integer overflow in OpenSSH XMSS key parsing in versions 7.7 through 7.9 and 8.x before 8.1. The CVE states exposure requires OpenSSH compiled and configured with the experimental XMSS key type; portable OpenSSH had no supported way to enable XMSS.

Likely exposure

Likely limited. Exposure depends on OpenSSH 7.7-7.9 or 8.x before 8.1 plus experimental XMSS support being compiled and used. Standard portable OpenSSH builds are less likely affected, but vendor appliances and distribution packages should be checked.

Exploitation context

The bundle does not show CISA KEV listing or confirmed active exploitation. Public advisory material describes the bug class and affected condition, but Glexia should not assume practical exploitation in normal deployments without verifying XMSS support.

Researcher notes

Focus analysis on build-time XMSS support and key parsing reachability. The OpenBSD diff and advisory references indicate the vulnerable area is sshkey-xmss.c. Avoid extrapolating to all OpenSSH deployments without proving XMSS support exists.

Mitigation direction

  • Upgrade OpenSSH to 8.1 or a vendor-patched package.
  • Check distribution and appliance advisories for product-specific fixes.
  • Disable or avoid XMSS key support where present.
  • Remove XMSS key material from SSH authentication paths if found.
  • Prioritize vendor guidance for embedded or appliance deployments.

Validation and detection

  • Inventory OpenSSH versions across servers, clients, and appliances.
  • Identify systems running OpenSSH 7.7-7.9 or 8.x before 8.1.
  • Confirm whether XMSS support was compiled into each build.
  • Review SSH configuration and key stores for XMSS key usage.
  • Map affected vendor products against NetApp, Gentoo, Siemens, and OS advisories.
Prepared
Confidence
high
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Execution behavior lookup

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CVE-2019-16905 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
10Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.