CVE-2025-69644

Executive Summary

CVE-2025-69644 is a denial-of-service (DoS) vulnerability in the GNU Binutils objdump utility, affecting versions prior to 2.46. The flaw resides in the handling of malformed DWARF debug information, specifically within the logic for processing location list headers. When objdump processes a crafted binary, it can enter an unbounded loop, generating endless output and consuming excessive CPU and memory resources until manually interrupted. This vulnerability is classified as a local attack vector, requiring the victim to run objdump on a malicious file. The CVSS score is 0.0 in the NVD data, but based on the description, a more accurate score is 5.5 (AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H). No public exploit code or proof-of-concept is currently available, and the patch is included in Binutils 2.46.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
• Base Score: 5.5 (Medium)
• Attack Vector: Local (AV:L) – The attacker must have local access to the system or trick a user into processing a malicious file.
• Attack Complexity: Low (AC:L) – No special conditions are required to trigger the vulnerability.
• Privileges Required: None (PR:N) – The attacker does not need any privileges.
• User Interaction: Required (UI:R) – The victim must run objdump on the malicious file.
• Scope: Unchanged (S:U) – The vulnerability does not affect other components.
• Confidentiality Impact: None (C:N)
• Integrity Impact: None (I:N)
• Availability Impact: High (A:H) – The vulnerability causes a denial of service by consuming resources.

Threat Level: Medium. The vulnerability is local and requires user interaction, but it can lead to significant resource exhaustion, potentially impacting system stability.

Deep Dive & Mechanics

The vulnerability is rooted in the DWARF debug information parsing logic within objdump. DWARF (Debugging With Attributed Record Formats) is a standardized debugging data format used in compiled binaries. The objdump utility uses this information to display debug-related content.

Specifically, the flaw exists in the handling of DWARF location list headers. Location lists are used to describe the location of variables over a range of program counters. Each location list entry has a header that defines the start and end offsets. A logic flaw in the parsing code fails to properly validate the header values, particularly when the start offset is greater than or equal to the end offset, or when the offsets are malformed in a way that causes the parser to never advance past the current entry.

When objdump encounters a crafted binary with such malformed location list headers, it enters an unbounded loop. Instead of moving to the next entry or terminating, it repeatedly processes the same header, generating endless output. This leads to:

• CPU Exhaustion: The loop consumes 100% CPU on a single core.
• Memory Exhaustion: The endless output can fill up disk space or memory buffers.
• Denial of Service: The process must be manually killed (e.g., with kill -9).

The vulnerability is triggered by the -Wl or --dwarf=loc options, which instruct objdump to display DWARF location lists. However, any invocation that processes debug information (e.g., objdump -d with debug sections) could potentially trigger the flaw.

Vulnerable vs. Patched Code

The vulnerable code is in the dwarf.c file of Binutils, specifically in the function that processes location list headers. The logic flaw is in the loop that iterates over location list entries.

Vulnerable Code (Conceptual):

// Vulnerable: No validation of header offsets
while (1) {
    read_location_list_header(&start, &end);
    if (start >= end) {
        // Missing check: should break or skip
        continue; // Infinite loop if start >= end
    }
    // Process entries between start and end
    // ...
}

Patched Code (Conceptual):

// Patched: Validate header offsets and break on invalid
while (1) {
    read_location_list_header(&start, &end);
    if (start >= end) {
        break; // Exit loop on invalid header
    }
    // Process entries between start and end
    // ...
}

The patch ensures that if the start offset is greater than or equal to the end offset, the loop terminates instead of continuing indefinitely. This prevents the unbounded loop.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A vulnerable version of Binutils (e.g., 2.40) installed on the target system.
• Ability to deliver a crafted binary to the victim (e.g., via email, download, or shared drive).

Steps:

1. Craft the Malicious Binary: Create a binary with malformed DWARF location list headers. This can be done by modifying a normal ELF binary's .debug_loc section using a hex editor or a custom script.
2. Deliver the Payload: Send the crafted binary to the victim, e.g., as a file named innocent_looking_binary.
3. Trigger the Vulnerability: The victim runs objdump -Wl innocent_looking_binary. The tool enters an infinite loop, consuming CPU and generating endless output.
4. Impact: The victim's system becomes unresponsive due to resource exhaustion. The process must be killed manually.

Example Command:

objdump -Wl malicious_binary

Note: No public exploit code is available. The above is a conceptual description.

Blue Team (Detection & Defense)

Detection:

• Monitor for objdump processes that run for an unusually long time or consume excessive CPU.
• Use process monitoring tools (e.g., top, htop, ps) to identify stuck objdump processes.
• Implement file scanning to detect malformed DWARF sections in binaries.

Defense:

• Patch: Upgrade to Binutils 2.46 or later.
• User Education: Warn users not to run objdump on untrusted files.
• Sandboxing: Run objdump in a sandboxed environment (e.g., Docker container with resource limits).
• Resource Limits: Use ulimit to limit CPU time or output size for objdump processes.

Example Resource Limit:

ulimit -t 10  # Limit CPU time to 10 seconds
objdump -Wl suspicious_file

Indicators of Compromise (IOCs)

• Process Name: objdump running for an extended period (e.g., > 30 seconds).
• CPU Usage: Single core at 100% for an extended period.
• Output Size: Rapidly growing output file or terminal buffer.
• File Hash: SHA256 of a known malicious binary (none publicly available).
• Network Activity: None (local vulnerability).
• Log Entries: System logs may show objdump process being killed by user or OOM killer.

Detection Engineering

YARA Rule

rule CVE_2025_69644_DWARF_Loop {
    meta:
        description = "Detects malformed DWARF location list headers in ELF binaries"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-69644"
    strings:
        $dwarf_loc = ".debug_loc"
        $malformed_header = { FF FF FF FF 00 00 00 00 }  // Example: start=0xFFFFFFFF, end=0x00000000
    condition:
        $dwarf_loc and $malformed_header
}

Sigma Rule

title: CVE-2025-69644 - Binutils objdump Infinite Loop
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects prolonged objdump execution indicative of CVE-2025-69644 exploitation
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image: /usr/bin/objdump
        CommandLine: '* -Wl *'
    condition: selection
    timeframe: 30s
falsepositives:
    - Legitimate use of objdump on large files
level: medium

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-69644 - Potential Binutils DoS via Malicious Binary Transfer"; flow:to_server; fileext:"elf"; content:"|2e 64 65 62 75 67 5f 6c 6f 63|"; distance:0; within:10; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Patch: Upgrade to Binutils 2.46 or later. This is the only complete fix.
2. Workaround: Avoid using objdump with the -Wl or --dwarf=loc options on untrusted files.
3. Resource Limits: Use ulimit to restrict CPU time and output size for objdump processes.

Long-Term Measures:

• Implement file scanning for malformed DWARF sections in binaries.
• Use sandboxing for all binary analysis tools.
• Monitor for anomalous objdump behavior.

Patch Details:

• The fix is included in Binutils 2.46. No specific commit hash is provided in the NVD data. Users should update to the latest version from the GNU Binutils repository.

Valters IT Signature This report was generated by Valters IT Cyber Threat Intelligence Division. For questions, contact threatintel@valters.it.