CVE intelligence and bounded remediation

CVE-2016-8858 — Openbsd Openssh security vulnerability

High CVSS 7.8

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."

Severity
High
CVSS
7.8 (2.0)
Published
2016-12-09
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-399, CWE-400

Affected products

  • openbsd / openssh / 6.8
  • openbsd / openssh / 6.9
  • openbsd / openssh / 7.0
  • openbsd / openssh / 7.1
  • openbsd / openssh / 7.2
  • openbsd / openssh / 7.3

Matched remediation archetype

Resource exhaustion and denial of service

This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.

Check exposure

  • Identify attacker-influenced work factors including input size, nesting, compression, fan-out, regex cost, allocation, recursion, retries, and connection lifetime.
  • Map per-request and shared CPU, memory, disk, descriptor, thread, queue, and downstream-service limits.
  • Determine whether authentication, tenancy, quotas, and rate controls apply before expensive processing begins.

Remediate safely

  • Bound input size, nesting, expansion, work, concurrency, queue depth, retries, and execution time before resource-intensive processing.
  • Release resources on every success, error, cancellation, and timeout path and use backpressure instead of unbounded buffering.
  • Update affected components and add small deterministic tests that assert resource ceilings rather than exhausting a host.

Authoritative sources

Complete CVE record and remediation plan

The detailed catalog view below loads this exact record, its source evidence, and the full seven-phase agentic change plan.