CVE-2025-11494

Executive Summary

CVE-2025-11494 is a low-severity (CVSS 3.3) out-of-bounds read vulnerability discovered in GNU Binutils version 2.45. The flaw resides in the _bfd_x86_elf_late_size_sections function within bfd/elfxx-x86.c, which is part of the linker component. An attacker with local access can trigger an out-of-bounds read, potentially leading to information disclosure or a denial of service. The exploit has been made public, and a patch is available. While the EPSS score is 0.0%, indicating low exploitation likelihood in the wild, the public availability of the exploit warrants immediate attention for systems using the affected version.

Supply Chain & Package Security

This vulnerability affects the GNU Binutils package, a critical component in many Linux distributions and development environments. It is not an NPM, PyPI, Go, or Ruby package, but its widespread use in build toolchains means it can impact downstream software supply chains. Organizations should verify their build environments and CI/CD pipelines are not using the vulnerable version.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
• Base Score: 3.3 (Low)
• Attack Vector: Local (AV:L) – Requires local access to the system.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – Impact is confined to the vulnerable component.
• Confidentiality Impact: None (C:N) – No data exposure.
• Integrity Impact: None (I:N) – No data modification.
• Availability Impact: Low (A:L) – Potential for denial of service.

Threat Level: Low. The vulnerability requires local access and only results in an out-of-bounds read, which typically leads to information disclosure or a crash. The public exploit increases the risk for environments where untrusted users have local access.

Deep Dive & Mechanics

The vulnerability is an out-of-bounds read in the _bfd_x86_elf_late_size_sections function of the GNU Binutils linker (BFD library). This function is responsible for sizing sections during the linking process. The flaw occurs when processing specially crafted ELF files, where the function reads beyond the bounds of an allocated buffer.

Root Cause: The function fails to properly validate the size or index of a data structure before accessing it. When processing a malicious ELF object file, the linker reads from an invalid memory location, leading to an out-of-bounds read.

Impact: An attacker can craft an ELF file that, when linked by the vulnerable version, causes the linker to read memory outside the intended buffer. This could leak sensitive information from the process's address space or cause a segmentation fault (denial of service).

Exploitability: The exploit is public and requires local access to the system. The attacker must be able to invoke the linker with a malicious input file. This is typical in scenarios where users can compile or link untrusted code.

Vulnerable vs. Patched Code

The patch commit b6ac5a8a5b82f0ae6a4642c8d7149b325f4cc60a addresses the out-of-bounds read by adding proper bounds checking before accessing the array.

Vulnerable Code (simplified):

// In _bfd_x86_elf_late_size_sections
some_type *array = ...;
int index = ...;
// No bounds check
value = array[index];

Patched Code (simplified):

// In _bfd_x86_elf_late_size_sections
some_type *array = ...;
int index = ...;
if (index < 0 || index >= array_size)
  return FALSE; // or handle error
value = array[index];

The patch ensures that the index is within the valid range before accessing the array, preventing the out-of-bounds read.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• GNU Binutils 2.45 installed.
• Ability to compile and run a C program or use a pre-built exploit.
• Local access to the target system.

Exploit Steps:

1. Create a malicious ELF file that triggers the vulnerability. The public exploit (if available) would typically generate such a file.
2. Run the linker with the malicious file as input:

   ld -o output malicious.o
   

3. The linker will crash or leak memory, confirming the vulnerability.

Example Exploit (Conceptual):

// This is a conceptual example. Actual exploit code may vary.
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main() {
    // Generate a malicious ELF file
    // ... (crafting logic)
    // Invoke linker
    system("ld -o /dev/null malicious.o");
    return 0;
}

Blue Team (Detection & Mitigation)

Detection:

• Monitor for crashes of the ld or collect2 processes.
• Use file integrity monitoring to detect unexpected ELF files in build directories.
• Enable core dumps and analyze them for out-of-bounds read patterns.

Mitigation:

• Apply the patch immediately by updating to a patched version of GNU Binutils.
• Restrict local access to trusted users only.
• Use sandboxing or containerization for build environments.

Indicators of Compromise (IOCs)

• File Hashes: (Specific malicious ELF files may have unique hashes; no known public samples yet.)
• Process Names: ld, collect2, as (if invoked during linking)
• Log Entries: Segmentation faults in linker logs, core dumps.
• Network: None (local vulnerability).
• Behavior: Unexpected crashes during linking of untrusted object files.

Detection Engineering

YARA Rule

rule CVE_2025_11494_OutOfBoundsRead {
    meta:
        description = "Detects malicious ELF files targeting CVE-2025-11494"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-11494"
    strings:
        $elf_magic = { 7f 45 4c 46 }  // ELF magic
        $trigger_pattern = { ?? ?? ?? ?? }  // Placeholder for specific pattern
    condition:
        $elf_magic at 0 and $trigger_pattern
}

Sigma Rule

title: CVE-2025-11494 Exploitation Attempt
id: cve-2025-11494-exploit
status: experimental
description: Detects potential exploitation of CVE-2025-11494 via linker crashes
author: Valters IT
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/ld'
        CommandLine|contains: 'malicious'
    condition: selection
falsepositives:
    - Legitimate use of files named 'malicious'
level: medium

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2025-11494 Potential Exploit Delivery"; content:"|7f 45 4c 46|"; depth:4; sid:1000001; rev:1;)

Remediation & Mitigation

1. Patch Immediately: Update GNU Binutils to a version that includes the fix (commit b6ac5a8a5b82f0ae6a4642c8d7149b325f4cc60a or later). For most distributions, this means updating the binutils package.

   # For Debian/Ubuntu
   sudo apt-get update && sudo apt-get install --only-upgrade binutils
   # For RHEL/CentOS
   sudo yum update binutils
   

2. Workaround: If patching is not immediately possible, restrict local access to the linker. Only allow trusted users to compile or link code.
3. Monitor: Implement the detection rules above to identify exploitation attempts.
4. Review Build Pipelines: Ensure CI/CD systems use patched versions of Binutils.

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