CVE-2026-33382

Executive Summary

CVE-2026-33382 is a high-severity Denial of Service (DoS) vulnerability affecting Grafana API endpoints. The flaw resides in the lack of request body size limits on several API endpoints, some of which are unauthenticated. An attacker can send oversized payloads that force excessive memory allocation, potentially exhausting system memory and causing a denial of service. The vulnerability has a CVSS score of 7.5 (High) and is classified under CWE-770 (Allocation of Resources Without Limits or Throttling). No public exploit code or proof-of-concept is currently available, and no patch has been released by the vendor. The EPSS score is 0.0%, indicating low exploitation likelihood at this time, but the risk remains significant for unpatched Grafana instances exposed to the internet.

Supply Chain & Package Security

Grafana is a widely used open-source analytics and monitoring platform, distributed as a binary, Docker image, and via package managers (e.g., APT, YUM). This vulnerability affects the core application, not a specific package dependency. However, organizations using Grafana in containerized environments should verify that their images are not vulnerable and monitor for updates from the vendor.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
• Base Score: 7.5 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: None (C:N)
• Integrity Impact: None (I:N)
• Availability Impact: High (A:H)

The threat level is High due to the ease of exploitation (no authentication required) and the potential for complete service disruption. The vulnerability is particularly dangerous for internet-facing Grafana instances.

Deep Dive & Mechanics

The vulnerability exists because several Grafana API endpoints do not enforce limits on the size of incoming request bodies. When an attacker sends a request with an extremely large payload (e.g., several gigabytes of data), the server attempts to allocate memory to process the request. Without proper throttling or size checks, this can lead to:

1. Memory Exhaustion: The server consumes all available RAM, causing the Grafana process to crash or become unresponsive.
2. System Instability: In severe cases, the operating system may kill the process or swap heavily, degrading overall system performance.
3. Denial of Service: Legitimate users are unable to access Grafana dashboards or APIs.

The affected endpoints include both authenticated and unauthenticated ones, meaning an attacker does not need valid credentials to trigger the DoS. The vulnerability is classified under CWE-770, which covers resource allocation without limits.

Vulnerable vs. Patched Code

Since no official patch is available, the following comparison is based on expected secure coding practices.

Vulnerable Code (Conceptual):

# Example of vulnerable endpoint handler
def handle_api_request(request):
    data = request.body.read()  # No size limit
    process_data(data)

Patched Code (Expected):

# Example of patched endpoint handler with size limit
MAX_BODY_SIZE = 10 * 1024 * 1024  # 10 MB
def handle_api_request(request):
    if request.content_length > MAX_BODY_SIZE:
        return HTTPStatus.REQUEST_ENTITY_TOO_LARGE
    data = request.body.read(MAX_BODY_SIZE)
    process_data(data)

The patched version checks the Content-Length header and limits the amount of data read from the request body, preventing excessive memory allocation.

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• A vulnerable Grafana instance (version unknown, but likely < 10.x or similar)
• Network access to the Grafana API (e.g., port 3000)

Exploitation Steps:

1. Identify Vulnerable Endpoints: Use a tool like curl or netcat to send a large payload to common Grafana API endpoints (e.g., /api/dashboards/db, /api/annotations, /api/alerts).

2. Craft a Large Payload: Generate a large string or binary data to send as the request body.

3. Send the Request:

   # Example using curl to send a 1GB payload
   dd if=/dev/zero bs=1M count=1024 | curl -X POST http://target:3000/api/dashboards/db --data-binary @-
   

4. Monitor Impact: Observe the Grafana server's memory usage spike and eventual crash or unresponsiveness.

Expected Outcome: The Grafana service becomes unavailable, and the server may run out of memory.

Blue Team (Defense & Detection)

Defensive Measures:

• Network-Level: Deploy a Web Application Firewall (WAF) or reverse proxy (e.g., Nginx, HAProxy) to limit request body sizes.

  # Nginx configuration to limit body size
  client_max_body_size 10m;
  

• Application-Level: If possible, apply a temporary patch or configuration change to limit request sizes (e.g., using a middleware).
• Monitoring: Set up alerts for high memory usage and large request sizes.

Detection Steps:

• Monitor Grafana logs for requests with abnormally large Content-Length headers.
• Use network monitoring tools to detect large outbound/inbound traffic to Grafana ports.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests with Content-Length headers exceeding 10 MB (or normal baseline).
  • Repeated POST requests to Grafana API endpoints with large payloads.
• System IOCs:
  • Sudden spike in memory usage by the Grafana process.
  • Grafana process crashes or becomes unresponsive.
  • System logs showing out-of-memory (OOM) killer events.
• Log IOCs:
  • Grafana logs containing entries like request body too large (if any logging exists) or errors related to memory allocation.

Detection Engineering

YARA Rule

rule CVE_2026_33382_Grafana_DoS {
    meta:
        description = "Detects large HTTP request bodies targeting Grafana API endpoints"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2026-33382"
    strings:
        $http_method = "POST"
        $grafana_path = /\/api\/(dashboards|annotations|alerts|datasources|org|user)/
        $large_body = { 00 00 00 00 }  // Placeholder for large payload detection
    condition:
        $http_method and $grafana_path and filesize > 10MB
}

Sigma Rule

title: CVE-2026-33382 - Grafana DoS via Large Request Body
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP requests with large body sizes targeting Grafana API endpoints
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem|startswith: '/api/'
        sc-bytes|gte: 10485760  # 10 MB
    condition: selection
falsepositives:
    - Legitimate large data uploads (e.g., dashboard imports)
level: high

Suricata Rule

alert http any any -> any 3000 (msg:"CVE-2026-33382 - Grafana DoS Large Request Body"; flow:to_server; content:"POST"; http_method; content:"/api/"; http_uri; pcre:"/\/api\/(dashboards|annotations|alerts|datasources|org|user)/"; byte_test:1,>,10485760,0,relative; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Limit Request Body Size: Configure a reverse proxy (Nginx, Apache, HAProxy) to enforce a maximum request body size (e.g., 10 MB).
2. Restrict Network Access: If possible, limit access to Grafana API endpoints to trusted IP addresses or VPN users.
3. Monitor and Alert: Set up monitoring for memory usage and large request sizes.

Long-Term Fix:

• Apply an official patch from Grafana when available.
• Upgrade to a patched version of Grafana once released.
• Implement application-level input validation and size limits.

Workarounds:

• Use a Web Application Firewall (WAF) to block requests with excessive body sizes.
• Disable unnecessary API endpoints if not required.

Valters IT