CVE-2021-41380 — RealVNC Viewer 6.21.406 allows remote VNC servers to cause a denial of service (application crash) via crafted RFB protocol data

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.