CVE-2023-38178

What it actually does

Remote unauthenticated attacker can trigger a denial of service condition that crashes or severely degrades the availability of the affected service.

Why it matters to the business

Service outages interrupt team collaboration and communications, leading to lost productivity and potential SLA breaches until the instance is restored.

How an attack unfolds

An attacker locates a reachable Mattermost server instance and sends specially crafted network requests that exploit the underlying DoS flaw, causing the process to terminate or become unresponsive without requiring authentication or user interaction.

How to fix it

Upgrade github.com/mattermost/mattermost/server/v8 to version 9.0.2 or 9.1.1 (or later) as soon as possible. If immediate upgrade is not feasible, restrict network access to the server and monitor for anomalous request patterns.

How to confirm the fix worked

Confirm the running binary or container image reports a fixed version string of 9.0.2 or 9.1.1; re-test the previously vulnerable endpoints with benign traffic to verify continued availability under load.

Typical attack path

1. Scan or enumerate publicly reachable Mattermost servers
2. Send crafted requests targeting the vulnerable code path
3. Observe service crash or sustained high resource consumption
4. Repeat to maintain denial of service

How to detect it

Review web server and application logs for repeated requests that precede sudden process termination or high CPU/memory spikes; correlate with crash dumps or container restart events.

What your security team should do

• Prioritize upgrade of all Mattermost server v8 deployments to 9.0.2 or 9.1.1 within the next maintenance window
• Add the fixed versions to internal dependency scanners and block builds using older releases
• Enable rate limiting and request validation at the reverse proxy layer as a temporary control