CVE-2025-69648

Executive Summary

CVE-2025-69648 is a denial-of-service (DoS) vulnerability in GNU Binutils readelf (up to version 2.45.1). The flaw resides in the DWARF parsing logic for .debug_rnglists sections. When processing a crafted binary with malformed DWARF data, readelf enters an infinite loop, repeatedly printing a warning message without making forward progress. This results in a non-terminating output loop that requires manual interruption (e.g., SIGINT). No memory corruption or code execution is possible. The vulnerability is classified as a logic flaw (CWE-835) and is exploitable only when a user runs readelf on a maliciously crafted file.

Supply Chain & Package Security

This vulnerability affects the GNU Binutils package, which is a core component of many Linux distributions and development toolchains. The package is distributed via official distribution repositories (e.g., apt, yum) and source tarballs from the GNU project. While the vulnerability is not remotely exploitable, it can be triggered in automated CI/CD pipelines or security scanning tools that process untrusted binaries. Supply chain risk is low, but organizations should ensure that Binutils is updated when a patch becomes available.

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 (AV): Local (L) – The attacker must provide a malicious file to the victim.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): Required (R) – The victim must run readelf on the malicious file.
• Scope (S): Unchanged (U) – The vulnerability does not affect other components.
• Confidentiality (C): None (N) – No data exposure.
• Integrity (I): None (N) – No data modification.
• Availability (A): High (H) – The tool becomes unresponsive, causing a denial of service.

Threat Level: Medium. Exploitation requires user interaction and local access. The impact is limited to availability.

Deep Dive & Mechanics

The vulnerability is in the DWARF parsing code of readelf, specifically in the handling of the .debug_rnglists section. This section contains range list entries used for debug information. The parsing logic iterates over entries in the section. A logic flaw causes the parser to fail to advance the read pointer when encountering a malformed entry. Instead of skipping the entry or terminating with an error, it prints a warning and retries the same entry, leading to an infinite loop.

Root Cause: The loop condition does not check for progress after a warning. The code path for malformed data does not increment the offset, causing the same data to be processed repeatedly.

Trigger: A crafted ELF binary with a .debug_rnglists section containing an entry that violates the DWARF specification (e.g., an invalid range list header or a corrupted offset).

Impact: The readelf process consumes 100% CPU and never terminates. The output stream is flooded with repeated warning messages. The process must be killed manually (e.g., kill -9).

Vulnerable vs. Patched Code

The vulnerable code is in readelf.c (or dwarf.c) in the function that processes .debug_rnglists. The exact location is not publicly disclosed, but the logic is similar to:

// Vulnerable pseudo-code
while (offset < section_size) {
    unsigned char *entry = section_data + offset;
    if (is_malformed(entry)) {
        warn("Malformed entry at offset %lu", offset);
        // BUG: offset is not incremented
        continue; // Infinite loop
    }
    process_entry(entry);
    offset += entry_size(entry);
}

A patched version would increment the offset even on malformed entries:

// Patched pseudo-code
while (offset < section_size) {
    unsigned char *entry = section_data + offset;
    if (is_malformed(entry)) {
        warn("Malformed entry at offset %lu", offset);
        offset += 1; // Skip the malformed byte
        continue;
    }
    process_entry(entry);
    offset += entry_size(entry);
}

Exploitation & Lab Setup

Red Team

Objective: Cause a denial of service on a target system by tricking a user or automated tool into running readelf on a malicious binary.

Steps:

1. Craft the Malicious Binary: Use a tool like pwntools or a hex editor to modify a valid ELF binary. Inject a malformed .debug_rnglists section. The section must contain an entry that triggers the infinite loop (e.g., a range list header with an invalid length or a corrupted offset).

2. Deliver the Binary: Send the binary via email, file upload, or social engineering. The victim must execute readelf on it.

3. Trigger the Vulnerability: The victim runs:

   readelf --debug-dump=rnglists malicious_binary
   

   The tool will hang indefinitely, printing warnings.

Proof-of-Concept (No public exploit available):

# Example script to craft a malformed ELF (requires pyelftools)
from elftools.elf.elffile import ELFFile
from elftools.elf.sections import Section
import io

# This is a placeholder; actual crafting requires deep DWARF knowledge.
# The key is to create a .debug_rnglists section with a malformed entry.
print("No public PoC available. Crafting requires manual binary manipulation.")

Blue Team

Detection: Monitor for readelf processes that run for an unusually long time or consume excessive CPU. Use the Sigma rule below.

Mitigation: Avoid running readelf on untrusted binaries. Use sandboxed environments for binary analysis.

Hunting: Search for processes named readelf with high CPU usage and repeated warning messages in logs.

Indicators of Compromise (IOCs)

• Process: readelf running with high CPU usage for an extended period.
• Logs: Repeated warning messages in stdout/stderr: "Malformed entry at offset" (exact string may vary).
• File: An ELF binary with a malformed .debug_rnglists section.
• Network: None (local vulnerability).

Detection Engineering

YARA Rule

rule CVE_2025_69648_Readelf_Infinite_Loop {
    meta:
        description = "Detects ELF binaries with malformed .debug_rnglists section triggering CVE-2025-69648"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-69648"
    strings:
        $rnglists = ".debug_rnglists"
        $malformed = { ?? ?? ?? ?? } // Placeholder for malformed entry pattern
    condition:
        $rnglists and #malformed > 0
}

Sigma Rule

title: CVE-2025-69648 - Readelf Infinite Loop Detection
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects readelf processes stuck in an infinite loop due to malformed DWARF data.
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/readelf'
        CommandLine|contains: '--debug-dump=rnglists'
    condition: selection
    timeframe: 5m
    condition: selection and (duration > 300) // Process running >5 minutes
falsepositives:
    - Legitimate analysis of large binaries
level: medium

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2025-69648 - Readelf Infinite Loop Attempt"; flow:to_server; content:"|2e 64 65 62 75 67 5f 72 6e 67 6c 69 73 74 73|"; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Do not run readelf on untrusted binaries. Use sandboxed environments (e.g., Docker, VMs) for binary analysis.
2. Monitor for abnormal readelf behavior using the provided Sigma rule.
3. Kill stuck processes with kill -9 <PID>.

Long-term Fix:

• Wait for a patch from GNU Binutils. The fix will likely be in a future release (e.g., 2.46). Apply the patch as soon as it is available.
• Consider using alternative tools like llvm-dwarfdump for DWARF analysis.

Workaround:

• Use timeout to limit execution time:

  timeout 10 readelf --debug-dump=rnglists suspicious_binary
  

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert