CVE-2025-2915

Executive Summary

CVE-2025-2915 is a heap-based buffer overflow vulnerability in the HDF5 library, up to version 1.14.6. The flaw resides in the H5F__accum_free function within src/H5Faccum.c, where improper handling of the overlap_size argument can lead to memory corruption. With a CVSS score of 3.3 (Low), the attack vector is local, requiring an attacker to execute a specially crafted HDF5 file or script on the target system. The exploit has been publicly disclosed, increasing the risk of weaponization despite the low EPSS score (0.0%). No official patch is available at this time.

Supply Chain & Package Security

HDF5 is a widely used data model and file format for storing and managing large amounts of data, commonly integrated into scientific computing, machine learning, and big data pipelines. This vulnerability affects any application or system that processes HDF5 files using the vulnerable library. Since HDF5 is often distributed as a system package or bundled with software, the supply chain risk is moderate. Users should monitor for updates from their package managers (e.g., apt, yum, conda) and consider isolating HDF5 processing in sandboxed environments until a patch is released.

CVSS Breakdown & Threat Level

• CVSS Score: 3.3 (Low)
• Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
• Attack Vector (AV): Local – the attacker must have local access to the system.
• Attack Complexity (AC): Low – no special conditions required.
• Privileges Required (PR): Low – attacker needs basic user privileges.
• User Interaction (UI): None – no user action needed beyond executing the exploit.
• Scope (S): Unchanged – the vulnerability does not affect other components.
• Confidentiality (C): None – no data exposure.
• Integrity (I): None – no data modification.
• Availability (A): Low – can cause a denial of service or crash.

Threat Level: Low, but with public exploit code, the risk of targeted attacks increases. The vulnerability is not remotely exploitable, limiting its impact to local privilege escalation or denial of service.

Deep Dive & Mechanics

The vulnerability is a heap-based buffer overflow in the H5F__accum_free function of HDF5's metadata accumulator. The function is responsible for managing free space in the file's metadata cache. When processing a crafted HDF5 file, the overlap_size parameter is manipulated to cause an out-of-bounds write on the heap.

Technical Details:

• Function: H5F__accum_free in src/H5Faccum.c
• Root Cause: The function does not properly validate the overlap_size argument against the allocated buffer size. An attacker can supply a value that exceeds the buffer boundaries, leading to a heap overflow.
• Impact: Memory corruption can lead to application crashes (denial of service) or potentially arbitrary code execution if combined with other vulnerabilities. However, due to the local attack vector and low privileges required, the primary risk is denial of service.

Exploit Mechanism:

1. The attacker crafts a malicious HDF5 file with specific metadata that triggers the vulnerable code path.
2. When the file is opened and processed by an application using the vulnerable HDF5 library, the H5F__accum_free function is called with a manipulated overlap_size.
3. The function writes data beyond the allocated heap buffer, corrupting adjacent memory.
4. This can cause the application to crash or behave unpredictably.

Vulnerable vs. Patched Code

Since no official patch is available, the vulnerable code is present in HDF5 versions up to 1.14.6. The following is a simplified representation of the vulnerable code pattern:

Vulnerable Code (src/H5Faccum.c):

// Vulnerable: no bounds check on overlap_size
void H5F__accum_free(H5F_t *f, haddr_t addr, hsize_t size) {
    // ... 
    size_t overlap_size = compute_overlap(addr, size);
    // Directly uses overlap_size without validation
    memcpy(accum->buffer + offset, source, overlap_size);
    // ...
}

Patched Code (Hypothetical):

// Patched: added bounds check
void H5F__accum_free(H5F_t *f, haddr_t addr, hsize_t size) {
    // ...
    size_t overlap_size = compute_overlap(addr, size);
    if (overlap_size > accum->buffer_size - offset) {
        // Handle error or truncate
        overlap_size = accum->buffer_size - offset;
    }
    memcpy(accum->buffer + offset, source, overlap_size);
    // ...
}

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• Local access to a system with HDF5 library version <= 1.14.6.
• Ability to create or deliver a malicious HDF5 file.

Exploit Steps:

1. Craft Malicious HDF5 File: Use a hex editor or custom script to create an HDF5 file with manipulated metadata that triggers the overflow. The exact payload depends on the memory layout.
2. Deliver File: Place the file on the target system (e.g., via email, USB, or network share).
3. Trigger Vulnerability: Open the file with any application that uses the vulnerable HDF5 library (e.g., h5dump, h5ls, or a custom program).
4. Observe Crash: The application may crash, or if combined with heap spraying, arbitrary code execution might be possible.

Example (Conceptual):

# Python script to generate a malicious HDF5 file (simplified)
import h5py
import numpy as np

# Create a normal file first
with h5py.File('malicious.h5', 'w') as f:
    f.create_dataset('data', data=np.zeros((100, 100)))

# Then modify the file to trigger the overflow (requires low-level manipulation)
# This is a placeholder for actual exploit logic

Blue Team (Defensive)

Detection:

• Monitor for crashes in applications using HDF5 (e.g., h5dump, h5ls, scientific software).
• Use file integrity monitoring to detect unexpected HDF5 files.
• Enable heap corruption detection tools (e.g., AddressSanitizer, Valgrind) in development environments.

Mitigation:

• Restrict local access to trusted users only.
• Use sandboxing or containerization for HDF5 processing.
• Apply vendor patches when available.
• Consider using alternative libraries or file formats if possible.

Indicators of Compromise (IOCs)

• File Hashes (Malicious HDF5): (Placeholder – actual hashes depend on exploit)
  • SHA256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
• Process Anomalies:
  • Unexpected crashes in h5dump, h5ls, or other HDF5 tools.
  • Heap corruption errors in system logs.
• Network: None (local vulnerability).
• Registry/File System: Presence of unusual HDF5 files in user directories.

Detection Engineering

YARA Rule

rule CVE_2025_2915_HDF5_HeapOverflow {
    meta:
        description = "Detects malicious HDF5 files exploiting CVE-2025-2915"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-2915"
    strings:
        $hdf5_magic = { 89 48 44 46 0D 0A 1A 0A } // HDF5 magic bytes
        $overlap_pattern = { ?? ?? ?? ?? ?? ?? ?? ?? } // Placeholder for specific exploit pattern
    condition:
        $hdf5_magic at 0 and $overlap_pattern
}

Sigma Rule

title: CVE-2025-2915 HDF5 Heap Overflow Exploit Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects potential exploitation of CVE-2025-2915 via HDF5 file processing
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\h5dump.exe'
            - '\h5ls.exe'
            - '\h5repack.exe'
        CommandLine|contains: 'malicious.h5'
    condition: selection
falsepositives:
    - Legitimate use of HDF5 tools with similar filenames
level: medium

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-2915 HDF5 Heap Overflow Attempt"; flow:to_server,established; content:"|89 48 44 46 0D 0A 1A 0A|"; depth:8; content:"|00 00 00 00|"; distance:0; within:4; reference:cve,2025-2915; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Restrict Local Access: Limit user privileges to prevent exploitation.
2. Monitor for Exploits: Use the provided detection rules to identify malicious HDF5 files.
3. Sandbox Processing: Run HDF5 file processing in isolated environments (e.g., Docker containers with read-only filesystems).

Long-Term Fix:

• Apply vendor patches when released. Monitor the HDF5 project page (https://www.hdfgroup.org/) for updates.
• Consider upgrading to a patched version once available.
• If possible, switch to alternative data formats (e.g., NetCDF, Zarr) that are not affected.

Workaround:

• Disable or restrict the use of HDF5 tools on critical systems until a patch is applied.

Valters IT