CVE-2024-7983: Open WebUI Markdown DoS Vulnerability

CVE-2024-7983 Overview

CVE-2024-7983 affects open-webui version 0.3.8 and exposes an unauthenticated endpoint that converts markdown to HTML. Attackers can submit maliciously crafted markdown payloads that force the server into excessive processing. The server becomes unresponsive to all other requests until the conversion completes, producing a denial of service condition.

The vulnerability maps to [CWE-770: Allocation of Resources Without Limits or Throttling]. Because the endpoint requires no authentication, any network-reachable attacker can trigger the condition remotely. Open-WebUI is a widely deployed self-hosted interface for large language model backends, which increases exposure across research, enterprise, and hobbyist deployments.

Critical Impact
An unauthenticated remote attacker can render an open-webui 0.3.8 instance unresponsive by sending a crafted markdown payload to the conversion endpoint.

Affected Products

openwebui/open_webui version 0.3.8
Self-hosted open-webui deployments exposing the markdown-to-HTML endpoint
Downstream distributions bundling open-webui 0.3.8

Discovery Timeline

2025-03-20 - CVE-2024-7983 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-7983

Vulnerability Analysis

Open-WebUI exposes an HTTP endpoint that converts user-supplied markdown into HTML. In version 0.3.8, this endpoint accepts requests without authenticating the caller and without bounding the resources consumed by the parser. An attacker submits a markdown document constructed to trigger pathological parsing behavior in the conversion routine.

The parser then spends excessive CPU time processing the input. Because the request handler executes synchronously in the server's request loop, all concurrent requests queue behind the running conversion. Legitimate users observe timeouts, failed logins, and unresponsive chat sessions. Repeating the request keeps the service in a degraded state for as long as the attacker maintains the traffic.

Root Cause

The root cause is missing input constraints and missing authentication on the conversion endpoint. The service does not cap input size, enforce a parse timeout, or limit concurrent conversions per client. Combined with unauthenticated access, these gaps satisfy the conditions described in [CWE-770] for uncontrolled resource allocation.

Attack Vector

Exploitation requires only network access to the open-webui HTTP interface. The attacker sends an HTTP request containing a crafted markdown payload to the conversion route. No credentials, user interaction, or prior foothold are required. A single request is sufficient to stall the server, and repeated requests sustain the outage. Details of the reproduction path are documented in the Huntr Bounty Report.

No verified public exploit code is available. The vulnerability is described in prose here rather than reproduced, consistent with the absence of a published proof-of-concept in the referenced advisory.

Detection Methods for CVE-2024-7983

Indicators of Compromise

Sustained single-request CPU saturation on the open-webui process without corresponding user activity
HTTP POST requests to the markdown conversion endpoint originating from unauthenticated sources
Repeated inbound requests with unusually large or deeply nested markdown bodies
Application logs showing long-running conversion handlers followed by request queue backlogs

Detection Strategies

Alert on open-webui request handler duration exceeding a defined threshold, for example 5 seconds
Baseline the size distribution of requests to the markdown endpoint and flag statistical outliers
Correlate spikes in /api/* latency with concurrent inbound requests from the same source IP
Monitor for unauthenticated access patterns against endpoints that should require a session

Monitoring Recommendations

Ingest open-webui access and error logs into a centralized logging platform for query and correlation
Track process-level CPU and memory usage of the open-webui container or service
Configure availability probes against the web interface to detect service stalls
Retain network flow records to identify source IPs generating repeated conversion requests

How to Mitigate CVE-2024-7983

Immediate Actions Required

Upgrade open-webui to a release later than 0.3.8 that addresses the unauthenticated conversion endpoint
Restrict network access to the open-webui interface using firewall rules or reverse-proxy allowlists
Place open-webui behind an authenticating reverse proxy that enforces request size and rate limits
Audit deployment inventories to identify any instance still running version 0.3.8

Patch Information

Refer to the Huntr Bounty Report for the disclosure record. The vendor advisory listing was not populated in the NVD entry at publication. Operators should track the open-webui project releases and apply the first fixed version above 0.3.8 referenced by the project maintainers.

Workarounds

Block or rate-limit requests to the markdown-to-HTML endpoint at a reverse proxy such as NGINX or Traefik
Enforce a maximum request body size on the proxy to reject oversized markdown payloads
Require authentication at the proxy layer for every route until the upgrade is complete
Run open-webui with CPU and memory cgroup limits to contain the impact of a single abusive request

bash

# NGINX reverse-proxy example limiting body size and request rate
limit_req_zone $binary_remote_addr zone=owui:10m rate=5r/s;

server {
    listen 443 ssl;
    server_name openwebui.example.com;

    client_max_body_size 64k;

    location / {
        limit_req zone=owui burst=10 nodelay;
        auth_basic "open-webui";
        auth_basic_user_file /etc/nginx/.htpasswd;
        proxy_read_timeout 5s;
        proxy_pass http://127.0.0.1:8080;
    }
}