CVE-2025-31176

Executive Summary

CVE-2025-31176 describes a denial-of-service vulnerability in Gnuplot, a widely used portable command-line driven graphing utility. The flaw resides in the plot3d_points() function, which can be triggered to cause a segmentation fault, leading to a system crash. The vulnerability has a CVSS score of 0.0, indicating that no official CVSS vector has been assigned, and the EPSS score is 0.0%, suggesting very low exploitation activity in the wild. No public proof-of-concept (PoC) code, exploit-db entries, or nuclei templates are currently available. The patch status is unknown, and no official fix has been released by the vendor.

This vulnerability is a classic memory safety issue that can be leveraged by an attacker to crash the Gnuplot application, potentially leading to a denial of service. Given the lack of a patch and the low exploitation probability, the immediate risk is limited, but organizations using Gnuplot in automated or critical workflows should monitor for updates.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (Not yet assigned)
• CVSS Vector: UNKNOWN
• Attack Vector (AV): UNKNOWN
• Attack Complexity (AC): UNKNOWN
• Privileges Required (PR): UNKNOWN
• User Interaction (UI): UNKNOWN
• Scope (S): UNKNOWN
• Confidentiality (C): UNKNOWN
• Integrity (I): UNKNOWN
• Availability (A): UNKNOWN
• EPSS Score: 0.0% (Very low probability of exploitation)
• Threat Level: Low (based on current information)

The lack of a CVSS vector and the low EPSS score suggest that this vulnerability is not currently a high-priority threat. However, the potential for a crash (denial of service) means it should not be ignored, especially in environments where Gnuplot is exposed to untrusted input.

Deep Dive & Mechanics

The vulnerability is located in the plot3d_points() function within Gnuplot's source code. This function is responsible for rendering 3D point plots. A segmentation fault (segfault) occurs when the function attempts to access memory that it is not permitted to, typically due to a null pointer dereference, buffer overflow, or use-after-free condition.

Root Cause Analysis:

• The plot3d_points() function likely processes user-supplied data (e.g., from a data file or command-line input) to generate 3D plots.
• A flaw in the input validation or memory management logic allows an attacker to craft a malicious input that causes the function to read or write to an invalid memory address.
• This results in a segmentation fault, crashing the Gnuplot process.

Attack Vector:

• An attacker could provide a specially crafted data file or command sequence to Gnuplot.
• If Gnuplot is used in a server or automated pipeline (e.g., generating graphs from user-submitted data), this could be exploited remotely.
• The crash could be used to disrupt services that depend on Gnuplot.

Impact:

• Denial of Service (DoS): The primary impact is a crash of the Gnuplot application, potentially affecting any system or service relying on it.
• No evidence of code execution or data exfiltration has been reported.

Vulnerable vs. Patched Code

Since no official patch is available, a direct comparison cannot be made. However, based on the nature of the vulnerability, the fix would likely involve:

• Adding input validation checks before processing data in plot3d_points().
• Ensuring proper bounds checking on arrays or buffers.
• Implementing null pointer checks before dereferencing pointers.
• Using safer memory management functions (e.g., strncpy instead of strcpy).

Hypothetical vulnerable code pattern:

void plot3d_points(data_t *data) {
    // No check if data is NULL
    for (int i = 0; i < data->num_points; i++) {
        // Potential out-of-bounds access if num_points is incorrect
        point_t *p = &data->points[i];
        // ...
    }
}

Hypothetical patched code pattern:

void plot3d_points(data_t *data) {
    if (data == NULL) {
        return; // Handle null pointer
    }
    if (data->num_points > MAX_POINTS) {
        return; // Bounds check
    }
    for (int i = 0; i < data->num_points; i++) {
        point_t *p = &data->points[i];
        // ...
    }
}

Exploitation & Lab Setup

Red Team (Exploitation)

Objective: Crash Gnuplot by triggering the vulnerability in plot3d_points().

Prerequisites:

• Gnuplot installed on the target system.
• Ability to pass a malicious data file or command to Gnuplot.

Steps:

1. Create a malicious data file (e.g., malicious.dat) with crafted content designed to trigger the segfault.
2. Run Gnuplot with the malicious file:

   gnuplot -e "plot 'malicious.dat' with points"
   

3. Observe the crash (segmentation fault).

Note: Since no public PoC exists, the exact payload is unknown. The above is a generic approach.

Blue Team (Defense & Detection)

Detection:

• Monitor for crashes of the gnuplot process (e.g., via system logs or process monitoring).
• Look for unusual input files or command-line arguments passed to Gnuplot.
• Use file integrity monitoring to detect creation of suspicious data files.

Mitigation:

• Restrict access to Gnuplot to trusted users only.
• If Gnuplot is used in a web application, sanitize all user input before passing it to Gnuplot.
• Consider using a sandbox or container to isolate Gnuplot processes.
• Monitor for updates from the Gnuplot project and apply patches when available.

Indicators of Compromise (IOCs)

• Process Crash: Segmentation fault in gnuplot process.
• Log Entries: System logs showing gnuplot terminated with signal SIGSEGV.
• File Artifacts: Malicious data files (e.g., .dat, .plt) with unusual content.
• Network Traffic: None expected (local vulnerability).

Example log entry:

kernel: [12345.678] gnuplot[1234]: segfault at 0 ip 00007f1234567890 sp 00007ff123456789 error 4 in libgnuplot.so[7f1234500000+2000]

Detection Engineering

YARA Rule

rule CVE_2025_31176_Gnuplot_Segfault {
    meta:
        description = "Detects potential exploitation of CVE-2025-31176 in Gnuplot"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-31176"
    strings:
        $s1 = "plot3d_points" ascii wide nocase
        $s2 = "segfault" ascii wide nocase
        $s3 = "gnuplot" ascii wide nocase
    condition:
        any of ($s*) and filesize < 10MB
}

Sigma Rule

title: Gnuplot Segmentation Fault Detection
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects segmentation faults in the gnuplot process, potentially indicating exploitation of CVE-2025-31176.
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-31176
logsource:
    product: linux
    service: syslog
detection:
    selection:
        - "gnuplot.*segfault"
        - "gnuplot.*SIGSEGV"
    condition: selection
falsepositives:
    - Legitimate crashes due to other bugs
level: medium

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2025-31176 Gnuplot Potential Exploitation"; flow:to_server; content:"gnuplot"; nocase; content:"plot3d_points"; nocase; sid:1000001; rev:1;)

Note: The Suricata rule is generic and may generate false positives. It should be tuned based on the environment.

Remediation & Mitigation

1. Patch Status: No official patch is available. Monitor the Gnuplot project (http://www.gnuplot.info/) for updates.
2. Workaround: Avoid using the plot3d_points() function with untrusted data. If possible, use alternative plotting functions.
3. Access Control: Restrict execution of Gnuplot to trusted users and processes.
4. Sandboxing: Run Gnuplot in a container or sandbox to limit the impact of a crash.
5. Input Validation: If Gnuplot is used in a web application, implement strict input validation and sanitization before passing data to Gnuplot.
6. Monitoring: Implement detection rules (YARA, Sigma, Suricata) to identify potential exploitation attempts.

Valters IT Signature

This report was generated by Valters IT Cyber Threat Intelligence Division.