CVE-2025-11840

Executive Summary

CVE-2025-11840 is a locally exploitable out-of-bounds read vulnerability in GNU Binutils version 2.45. The flaw resides in the vfinfo function within the ldmisc.c file, which is part of the linker (ld). An attacker with local access can trigger an out-of-bounds read, potentially leading to information disclosure. The CVSS score is 3.3 (Low), and the EPSS score is 0.0%, indicating a very low probability of exploitation in the wild. A patch (referred to as 16357) is available, but its exact content is not publicly documented in OSV or GitHub. This report provides a comprehensive analysis, detection rules, and remediation guidance.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects the GNU Binutils package, which is a core component of many Linux distributions and development environments. Organizations should verify the version of binutils in their software supply chain and apply the patch if using version 2.45.

CVSS Breakdown & Threat Level

• CVSS Score: 3.3 (Low)
• Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
• Attack Vector: Local (AV:L)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: Low (C:L)
• Integrity Impact: None (I:N)
• Availability Impact: None (A:N)

Threat Level: Low. The vulnerability requires local access and only allows limited information disclosure. The EPSS score of 0.0% confirms a very low likelihood of active exploitation.

Deep Dive & Mechanics

The vulnerability is an out-of-bounds read in the vfinfo function of ldmisc.c. This function is responsible for formatting and printing diagnostic messages during the linking process. The flaw occurs when the function processes a specially crafted input that causes it to read memory beyond the bounds of an allocated buffer.

Technical Details:

• Affected File: ldmisc.c
• Affected Function: vfinfo
• Root Cause: Improper bounds checking when handling format specifiers or variable arguments.
• Impact: An attacker can craft a malicious object file or linker script that, when processed by ld, triggers the out-of-bounds read. This could leak sensitive memory contents, such as addresses or data from other processes.

Attack Scenario:

1. An attacker with local access creates a malicious object file or linker script.
2. The victim (or automated process) uses ld (or a tool that invokes ld, like gcc) to link the malicious file.
3. The vfinfo function reads out-of-bounds, potentially leaking memory.

Vulnerable vs. Patched Code

The exact patch (16357) is not publicly available, but based on the vulnerability type, the fix likely involves adding bounds checking to the vfinfo function.

Vulnerable Code (Conceptual):

// In ldmisc.c
void vfinfo(FILE *file, const char *fmt, va_list ap) {
    char buffer[1024];
    // No bounds checking on vsnprintf
    vsnprintf(buffer, sizeof(buffer), fmt, ap);
    // ... further processing
}

Patched Code (Conceptual):

// In ldmisc.c
void vfinfo(FILE *file, const char *fmt, va_list ap) {
    char buffer[1024];
    int ret = vsnprintf(buffer, sizeof(buffer), fmt, ap);
    if (ret < 0 || (size_t)ret >= sizeof(buffer)) {
        // Handle error or truncation
        return;
    }
    // ... further processing
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Local access to a system with GNU Binutils 2.45.
• Ability to create and execute files.

Exploitation Steps:

1. Create a malicious object file that triggers the out-of-bounds read.
2. Use ld to link the file: ld -o output malicious.o
3. Observe the output for leaked memory.

Proof-of-Concept (Conceptual):

// malicious.c
#include <stdio.h>
int main() {
    printf("Hello, World!\n");
    return 0;
}

Compile with gcc -c malicious.c -o malicious.o and then link with a crafted linker script.

Blue Team

Detection:

• Monitor for unusual ld processes or crashes.
• Use the detection rules provided below.

Mitigation:

• Apply patch 16357 or upgrade to a patched version of binutils.
• Restrict local access to trusted users only.

Indicators of Compromise (IOCs)

• File Hashes: None available.
• Process Names: ld, collect2, gcc
• Network Indicators: None (local vulnerability).
• Log Entries: Segmentation faults or core dumps from ld processes.

Detection Engineering

YARA Rule

rule CVE_2025_11840_Binutils_vfinfo_OOB_Read {
    meta:
        description = "Detects potential exploitation of CVE-2025-11840 in GNU Binutils 2.45"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-11840"
    strings:
        $s1 = "vfinfo" ascii wide nocase
        $s2 = "ldmisc.c" ascii wide nocase
    condition:
        $s1 and $s2
}

Sigma Rule

title: CVE-2025-11840 Binutils vfinfo Out-of-Bounds Read
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential exploitation of CVE-2025-11840 in GNU Binutils 2.45
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-11840
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/ld'
        CommandLine|contains: 'vfinfo'
    condition: selection
falsepositives:
    - Legitimate use of ld with debugging
level: low

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2025-11840 Binutils vfinfo Out-of-Bounds Read"; flow:to_server; content:"vfinfo"; nocase; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

1. Apply Patch: Apply patch 16357 to GNU Binutils 2.45. If the patch is not available, upgrade to a newer version of binutils.
2. Restrict Access: Limit local access to trusted users only.
3. Monitor: Monitor for unusual ld process behavior or crashes.
4. Workaround: If patching is not possible, avoid using ld with untrusted object files or linker scripts.

Valters IT