CVE-2025-0312: Ollama DoS Vulnerability via GGUF Model

CVE-2025-0312 Overview

A null pointer dereference vulnerability exists in Ollama versions 0.3.14 and earlier that allows malicious actors to cause a Denial of Service (DoS) condition. The vulnerability occurs when a specially crafted GGUF model file is uploaded and processed by the Ollama server. Due to insufficient null pointer validation during model file parsing, an attacker can trigger a server crash, disrupting AI inference services for all users.

Critical Impact

Remote attackers can crash Ollama servers by uploading malicious GGUF model files, causing complete service disruption without requiring authentication.

Affected Products

• Ollama versions <=0.3.14
• All platforms running vulnerable Ollama server instances
• Self-hosted Ollama deployments exposed to untrusted model uploads

Discovery Timeline

• 2025-03-20 - CVE-2025-0312 published to NVD
• 2025-03-28 - Last updated in NVD database

Technical Details for CVE-2025-0312

Vulnerability Analysis

This vulnerability stems from CWE-476 (NULL Pointer Dereference), a memory corruption flaw that occurs when the application attempts to use a pointer that has a null value. In the context of Ollama, the GGUF model file parser fails to properly validate pointer values before dereferencing them during the model loading process.

When a malicious GGUF file is crafted with specific malformed structures, the parser encounters unexpected null values in data structures that should contain valid memory references. The subsequent attempt to access memory through these null pointers causes the server process to crash immediately. This vulnerability is particularly dangerous because GGUF is the primary model format used by Ollama for loading and running large language models.

The attack requires network access to the Ollama server's API endpoint that handles model uploads or creation. No authentication is required in default configurations, making this vulnerability trivially exploitable in exposed deployments.

Root Cause

The root cause of CVE-2025-0312 lies in insufficient input validation within the GGUF file parsing logic. The vulnerability occurs because:

1. The GGUF parser does not validate certain pointer values before dereferencing them
2. Malformed model files can contain structures that result in null pointer assignments
3. Error handling does not catch null pointer conditions before memory access operations
4. The server lacks defensive programming patterns such as null checks before pointer dereferencing

This type of vulnerability is common in native code parsers that process complex binary file formats without rigorous bounds and null checking.

Attack Vector

The attack vector is network-based, allowing remote exploitation without user interaction. An attacker exploits this vulnerability through the following sequence:

1. The attacker crafts a malicious GGUF model file with structures designed to trigger null pointer conditions during parsing
2. The attacker uploads the malicious model file to the Ollama server using the model creation API
3. When the server attempts to parse and load the model, it encounters the null pointer
4. The null pointer dereference causes the Ollama server process to crash
5. All ongoing inference requests are terminated, and the service becomes unavailable

The attack is reproducible and can be repeated to maintain a persistent denial of service condition. For detailed technical information about this vulnerability, refer to the Huntr Bounty Report.

Detection Methods for CVE-2025-0312

Indicators of Compromise

• Unexpected Ollama server process crashes or terminations
• Crash logs showing segmentation faults or null pointer access violations
• Unusual GGUF model file uploads from untrusted sources
• Repeated server restart events in system logs

Detection Strategies

• Monitor Ollama server process health and implement crash alerting
• Audit model upload requests for anomalous file sizes or patterns
• Implement rate limiting on model creation API endpoints
• Review system crash dumps for null pointer dereference signatures

Monitoring Recommendations

• Enable verbose logging on Ollama server instances to capture detailed error information
• Configure process monitoring to detect and alert on unexpected service terminations
• Implement network traffic analysis to identify suspicious model upload patterns
• Set up log aggregation to correlate crash events with incoming API requests

How to Mitigate CVE-2025-0312

Immediate Actions Required

• Upgrade Ollama to a version newer than 0.3.14 that contains the security fix
• Restrict access to model upload/creation API endpoints to trusted users only
• Implement network segmentation to limit exposure of Ollama servers
• Enable authentication on Ollama API endpoints if not already configured

Patch Information

Organizations should upgrade to the latest stable version of Ollama that addresses this null pointer dereference vulnerability. Review the official Ollama release notes for security-related updates and ensure all deployments are running patched versions.

For detailed information about this vulnerability and remediation guidance, consult the Huntr Bounty Report.

Workarounds

• Deploy a reverse proxy with authentication in front of Ollama API endpoints
• Restrict model upload capabilities to authenticated administrators only
• Implement input validation on model files before passing them to Ollama
• Use network firewall rules to limit access to the Ollama server from trusted IP ranges only

# Example: Restrict Ollama API access using iptables
# Allow only specific trusted IP ranges to access Ollama server port
iptables -A INPUT -p tcp --dport 11434 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 11434 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 11434 -j DROP