The kex_input_kexinit function in kex.c in OpenSSH 6.x and 7.x through 7.3 allows remote…
Priority MEDIUM 62CWE-400Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- No fix listed
Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA. Impact type from CWE-400.
Summary
The kex_input_kexinit function in kex.c in OpenSSH 6.x and 7.x through 7.3 allows remote attackers to cause a denial of service (memory consumption) by sending many duplicate KEXINIT requests. NOTE: a third party reports that "OpenSSH upstream does not consider this as a security issue."
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.29462 98th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | — | all versions | — | No fix listed | CNA |
- — Vendor— Affected all versions Fixed in — No fix listed CNA
CPE configurations NVD · 6
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:openbsd:openssh:6.8:*:*:*:*:*:*:* | 6.8 | Vulnerable | OpenBSD |
| cpe:2.3:a:openbsd:openssh:6.9:*:*:*:*:*:*:* | 6.9 | Vulnerable | OpenBSD |
| cpe:2.3:a:openbsd:openssh:7.0:*:*:*:*:*:*:* | 7.0 | Vulnerable | OpenBSD |
| cpe:2.3:a:openbsd:openssh:7.1:*:*:*:*:*:*:* | 7.1 | Vulnerable | OpenBSD |
| cpe:2.3:a:openbsd:openssh:7.2:*:*:*:*:*:*:* | 7.2 | Vulnerable | OpenBSD |
| cpe:2.3:a:openbsd:openssh:7.3:*:*:*:*:*:*:* | 7.3 | Vulnerable | OpenBSD |
- cpe:2.3:a:openbsd:openssh:6.8:*:*:*:*:*:*:* Versions 6.8 Vulnerable ·OpenBSD
- cpe:2.3:a:openbsd:openssh:6.9:*:*:*:*:*:*:* Versions 6.9 Vulnerable ·OpenBSD
- cpe:2.3:a:openbsd:openssh:7.0:*:*:*:*:*:*:* Versions 7.0 Vulnerable ·OpenBSD
- cpe:2.3:a:openbsd:openssh:7.1:*:*:*:*:*:*:* Versions 7.1 Vulnerable ·OpenBSD
- cpe:2.3:a:openbsd:openssh:7.2:*:*:*:*:*:*:* Versions 7.2 Vulnerable ·OpenBSD
- cpe:2.3:a:openbsd:openssh:7.3:*:*:*:*:*:*:* Versions 7.3 Vulnerable ·OpenBSD
Remediation
No fixed version listed by the sources yet.
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
Not affected: 3 products
- Red Hat Enterprise Linux 5
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
Timeline
- 2026-10-02 Threatist record created from CVE-2016-8858
- 2026-10-03 Alias added: GHSA-cfx4-r6f2-m2mc
References
Patch 2
Advisory 7
- [oss-security] 20161020 Re: Re: CVE Request: OpenSSH: Memory exhaustion issue found in OpenSSH
- https://security.netapp.com/advisory/ntap-20180201-0001/
- [oss-security] 20161019 CVE Request: OpenSSH: Memory exhaustion issue found in OpenSSH
- http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/kex.c.diff?r1=1.126&r2=1.127&f=h
- FreeBSD-SA-16:33
- GLSA-201612-18
- http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/kex.c?rev=1.127&content-type=text/x-cvsweb-markup
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- TI-2024-05929 Openssh: regresshion - race condition in ssh allows rce/dos CVSS 3.1HIGH 8.1
- TI-2023-10601 OpenSSH server (sshd) 9.1 introduced a double-free vulnerability during… CVSS 3.1MEDIUM 6.5
- TI-2018-11033 OpenSSH through 7.7 is prone to a user enumeration vulnerability due to not delaying… CVSS 3.1MEDIUM 5.9
- TI-2016-08105 Untrusted search path vulnerability in ssh-agent.c in ssh-agent in OpenSSH before 7.4… CVSS 3.1HIGH 7.3
- TI-2023-28040 In ssh in OpenSSH before 9.6, OS command injection might occur if a user name or host… CVSS 3.1MEDIUM 6.5
Sources
- CVE-2016-8858 · CVE Program
- CVE-2016-8858 · NVD
- FIRST EPSS
- GHSA-cfx4-r6f2-m2mc · GitHub Advisory Database · CC BY 4.0
- CVE-2016-8858 · Red Hat security data · CC BY 4.0
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