CVE-2019-16905

CVE-2019-16905 is a high-severity vulnerability in Openbsd Openssh with a CVSS 3.x base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-190.

Key facts

• Severity: High (CVSS 3.x base score 7.8)
• CVSS v2: 4.4
• EPSS exploit prediction: 2% (80th percentile)
• Actively exploited: Not listed in CISA KEV
• Weakness: CWE-190
• Affected product: Openbsd Openssh
• Published: 2019-10-09
• Last modified: 2026-06-17

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.

Frequently asked questions

What is 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 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.

How severe is CVE-2019-16905?

CVE-2019-16905 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2019-16905 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (80th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-16905?

CVE-2019-16905 primarily affects Openbsd Openssh. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2019-16905?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2019-16905 published?

CVE-2019-16905 was published on 2019-10-09 and last updated on 2026-06-17.

References

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

Affected products (5)

• cpe:2.3:a:openbsd:openssh:*:*:*:*:*:*:*:*
• cpe:2.3:a:netapp:cloud_backup:-:*:*:*:*:*:*:*
• cpe:2.3:a:netapp:steelstore_cloud_integrated_storage:-:*:*:*:*:*:*:*
• cpe:2.3:o:siemens:scalance_x204rna_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:siemens:scalance_x204rna_ecc_firmware:*:*:*:*:*:*:*:*

More vulnerabilities in Openbsd Openssh

• CVE-2003-0786 — Critical (CVSS 10.0): The SSH1 PAM challenge response authentication in OpenSSH 3.7.1 and 3.7.1p1, when Privilege Separation is disabled,…
• CVE-2003-0693 — Critical (CVSS 10.0): A "buffer management error" in buffer_append_space of buffer.c for OpenSSH before 3.7 may allow remote attackers to…
• CVE-2002-0640 — Critical (CVSS 10.0): Buffer overflow in sshd in OpenSSH 2.3.1 through 3.3 may allow remote attackers to execute arbitrary code via a large…
• CVE-2001-0144 — Critical (CVSS 10.0): CORE SDI SSH1 CRC-32 compensation attack detector allows remote attackers to execute arbitrary commands on an SSH…
• CVE-2000-0999 — Critical (CVSS 10.0): Format string vulnerabilities in OpenBSD ssh program (and possibly other BSD-based operating systems) allow attackers…
• CVE-2000-0525 — Critical (CVSS 10.0): OpenSSH does not properly drop privileges when the UseLogin option is enabled, which allows local users to execute…

All CVEs affecting Openbsd Openssh →

Other CWE-190 (Integer Overflow or Wraparound) vulnerabilities

• CVE-2026-4689 — Critical (CVSS 10.0): Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability was…
• CVE-2026-24814 — Critical (CVSS 10.0): Integer Overflow or Wraparound vulnerability in swoole swoole-src (thirdparty/hiredis modules). This vulnerability is…
• CVE-2025-64721 — Critical (CVSS 10.0): Sandboxie is a sandbox-based isolation software for 32-bit and 64-bit Windows NT-based operating systems. In versions…
• CVE-2015-5108 — Critical (CVSS 10.0): Integer overflow in Adobe Reader and Acrobat 10.x before 10.1.15 and 11.x before 11.0.12, Acrobat and Acrobat Reader DC…
• CVE-2015-5097 — Critical (CVSS 10.0): Integer overflow in Adobe Reader and Acrobat 10.x before 10.1.15 and 11.x before 11.0.12, Acrobat and Acrobat Reader DC…
• CVE-2013-2555 — Critical (CVSS 10.0): Integer overflow in Adobe Flash Player before 10.3.183.75 and 11.x before 11.7.700.169 on Windows and Mac OS X, before…

Browse all CWE-190 (Integer Overflow or Wraparound) vulnerabilities →

Threat intelligence

Threat-intel indicators referencing this CVE:

• 152.32.208.73 (ipv4-addr)
• 152.32.217.163 (ipv4-addr)
• 152.32.204.21 (ipv4-addr)
• 152.32.145.49 (ipv4-addr)
• 104.218.164.192 (ipv4-addr)
• 165.154.162.193 (ipv4-addr)
• 165.154.11.210 (ipv4-addr)
• 152.32.207.42 (ipv4-addr)