CVE-2025-69646

Executive Summary

CVE-2025-69646 is a denial-of-service (DoS) vulnerability in the GNU Binutils objdump utility, specifically within the handling of the DWARF debug_rnglists section. A local attacker can craft a malicious binary with a malformed debug_rnglists header that causes objdump to enter an unbounded logging loop, emitting the same warning message repeatedly and consuming excessive CPU and I/O resources until the process is manually terminated. The issue has been confirmed in binutils 2.44. This vulnerability is primarily a local availability concern for enterprise environments that routinely analyze untrusted binaries (e.g., malware analysts, CI/CD pipelines that run static analysis, and security research teams), as a single crafted file can halt automated analysis workflows.

Unlike vulnerabilities in network-facing services, this flaw requires the attacker to deliver a malicious file to the victim and persuade them to run objdump against it (or trigger it through an automated pipeline). The impact is limited to denial-of-service—there is no code execution or privilege escalation—but it can effectively stall security tooling, triage processes, and incident response workflows within an enterprise.

Technical Analysis

The vulnerability resides in the DWARF 5 debug_rnglists (range list) parser used by objdump. The debug_rnglists section stores address ranges used to map code addresses to source file/line information. The section begins with a header that includes a length field and a number of padding bytes. The parser reads this header to determine the offsets and boundaries of the range list entries that follow.

A logic error in how objdump handles the debug_rnglists header—specifically, the computation of the offset to the first entry or the termination condition for the range list traversal—causes the parser to fail to recognize the end of the list. Instead of terminating cleanly, the code enters a loop where it repeatedly attempts to parse the same malformed entry, prints a warning message (e.g., "invalid range list entry" or a similar diagnostic), and resets its state to the same byte offset, causing the warning to be emitted in a tight, unbounded loop.

The loop is triggered by the following conditions, typical of a crafted input file:

1. Malformed header length: The length field in the debug_rnglists header is set to a value inconsistent with the actual section size, causing the parser to read beyond the section boundary.
2. Invalid offset encoding: DWARF range list entries use a DW_RLE_offset_pair, DW_RLE_base_address, or DW_RLE_start_end encoding with a ULEB128 (unsigned LEB128) encoding for the offsets. A crafted ULEB128 sequence that decodes to a large value but leaves the parser in a state where the next entry's address computation produces the same offset can cause the parser to never advance.
3. Missing terminator: In the DWARF 5 format, the end of a range list is denoted by DW_RLE_end_of_list (value 0). If the crafted header misaligns the parser such that the 0x00 byte that should be the terminator is never encountered, the parser attempts to decode subsequent bytes as new range list entries, most of which are invalid—producing a warning and looping.

The key flaw is that the warning is printed to stderr on every iteration with no rate limiting, and the parser does not maintain a "seen before" state for the malformed offset, so it repeats the exact same sequence indefinitely.

The attack surface is any user or automated system that runs objdump on untrusted files. In enterprise contexts, this includes:

• Malware analysis sandboxes that call objdump to extract metadata from samples.
• CI/CD pipelines that use objdump to analyze build artifacts or validate binaries (e.g., checking for architecture, symbols, or embedded debug information).
• Security scanners that run objdump -x or objdump -s on files uploaded to a web-based analysis portal.
• SOC analysts manually triaging suspicious binaries.

The vulnerability is local, requiring the attacker to supply the malicious file. It does not require any special privileges—a standard user can generate the crafted binary and place it on a network share for an analyst to process.

Exploitation Scenarios

This vulnerability can be weaponized with minimal effort. The following is a step-by-step attack chain, assuming a real-world enterprise scenario where a security team uses objdump for binary triage, and the attacker seeks to degrade the team's analysis capability.

1) Reconnaissance and Target Identification

The attacker profiles the target environment to identify points where objdump is used. This is publicly inferable from:

• Job postings, blog posts, or conference talks by the target's security team that mention "we use objdump to analyze malware" or automated malware analysis pipelines.
• Web applications that accept file uploads for analysis and display disassembly or section information (revealing the use of objdump in the backend).
• Internal documentation or scripts leaked via public GitHub repositories that call objdump as a command-line step.

Alternatively, the attacker can use a generic phishing approach: craft the binary and email it to a security researcher at the target organization with a compelling subject line (e.g., "suspicious sample for review") so that an analyst manually runs objdump on it.

2) Trigger and Weaponization

The attacker creates a malicious binary that triggers the flaw. Steps to craft the payload (which can be done on any Linux system with binutils and a hex editor or Python):

#!/usr/bin/env python3
# craft_cve_2025_69646.py
import struct, sys

def uleb128(value):
    out = b''
    while True:
        byte = value & 0x7F
        value >>= 7
        if value:
            out += bytes([byte | 0x80])
        else:
            out += bytes([byte])
            return out

# Build a minimal ELF64 with a .debug_rnglists section containing malformed data
# ELF header (simplified — enough for objdump to parse sections)
# ... (in a real weaponized payload, this would be a valid ELF built from a real
#      DWARF-5-compiled binary, with only the .debug_rnglists section patched)

# The malicious .debug_rnglists section:
# Header: unit_length = 0xFFFFFFFF (invalid, larger than actual section size)
# version = 5, address_size = 8, seg_selector_size = 0
# offset_entry_count = 1, offset_base = 0x0
# Followed by a single DW_RLE_offset_pair entry:
#   encoding = 0x04 (DW_RLE_offset_pair)
#   x = 0x00, y = 0x00  (same offset — parser never advances)
# No terminator (DW_RLE_end_of_list = 0x00 missing)

malicious_rnglists = b''
malicious_rnglists += struct.pack('<I', 0xFFFFFFFF)  # unit_length: huge
malicious_rnglists += struct.pack('<H', 5)            # version (DWARF 5)
malicious_rnglists += struct.pack('<B', 8)            # address_size
malicious_rnglists += struct.pack('<B', 0)            # seg_selector_size
malicious_rnglists += struct.pack('<I', 1)            # offset_entry_count
malicious_rnglists += bytes(8)                        # offset_base (8 bytes)
malicious_rnglists += bytes([0x04])                   # DW_RLE_offset_pair
malicious_rnglists += uleb128(0)                      # x = 0
malicious_rnglists += uleb128(0)                      # y = 0

# ... (write to .debug_rnglists section of a valid ELF binary)
print("[*] Malicious binary written: /tmp/cve-2025-69646-malware.bin")

The attacker can automate this process by taking a legitimate ELF binary compiled with -gdwarf-5, locating the .debug_rnglists section with readelf -S, and overwriting it with the crafted bytes, adjusting the section header's sh_size to match. The resulting binary is a valid ELF that objdump will attempt to parse.

3) Payload/Execution

The attacker delivers the malicious binary to the victim:

• Email attachment disguised as a legitimate-looking binary (e.g., "firmware-update.bin" or "capture.filter").
• Network share on a file server that analysts mount for triage.
• Web upload to an analysis portal that automatically runs objdump.
• Phishing link that downloads the file to the analyst's workstation.

When the victim (or automated system) runs any of the following commands, the parser enters the loop:

objdump -x /path/to/malicious.bin
objdump -s /path/to/malicious.bin
objdump -S /path/to/malicious.bin

The process immediately begins emitting the same warning line to stderr and consuming 100% of a CPU core. If the system monitors process output, the massive stderr stream can fill log files, crash log rotation, and cause disk exhaustion on systems with small ephemeral disks.

4) Post-Exploitation Impact

• Analyst workstation: The analyst's terminal becomes unusable due to the flood of warnings; they must kill the process (Ctrl+C or kill -9), wasting time and potentially missing other indicators of compromise.
• Automated pipeline: The CI/CD job hangs indefinitely, blocking the pipeline and delaying all subsequent builds and analyses. If the runner has a timeout (e.g., 30 minutes), the job fails after that period but consumes significant CPU/dirty-I/O in between.
• Fleet-wide effect: If the malicious binary is uploaded to a shared analysis platform that fans out to multiple workers, every worker processing it enters the loop, causing a coordinated degradation of the analysis service.
• Log flood: The repeated warning messages written to stderr, if captured by a journal daemon (e.g., systemd-journald) or consumed by a log shipper (e.g., Filebeat), are forwarded to the SIEM, inflating event volume, consuming storage, and creating alert fatigue. A single malicious file can generate millions of identical log lines.

The attacker gains no code execution, but the availability degradation is sufficient to delay incident response and give the attacker time to operate undetected—for example, by submitting malware samples that the SOC would otherwise analyze quickly.

Impact Assessment

Business Impact: Denial-of-service. The affected component is a command-line utility, not an exposed service, so there is no direct internet-facing attack surface. However, in security operations centers and software development pipelines that automate binary analysis, the impact is a degradation of analysis throughput and potential system instability (CPU saturation, disk exhaustion from log flooding).

CVSS Arbitrary: The CVSS score is N/A, but assigning an arbitrary vector consistent with the vulnerability characteristics yields: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L (Local, Low complexity, No privileges required, User interaction required, Unchanged scope, No confidentiality impact, No integrity impact, Low availability impact). This places the severity at 3.1 (Low) per the standard qualitative scale.

Affected Systems:

• Linux and Unix workstations with binutils 2.44 installed (default on most mainstream distributions as of mid-2025).
• Cross-compilation toolchains that bundle binutils 2.44 for embedded development.
• CI/CD runners (Jenkins, GitLab CI, GitHub Actions) with binutils installed (near-universal on Linux runners).
• Security analysis platforms (VirusTotal, Hybrid Analysis, Intezer, and internal malware triage tools) if they invoke objdump for metadata extraction.
• The gdb, readelf, and addr2line tools are not affected—the flaw is specific to objdump's DWARF parser.

Blast Radius: Moderate. An attacker needs to deliver a file to the victim; the impact is limited to a local DoS on a single process. However, in contexts where one file is processed by multiple tools or queued across multiple workers, the blast radius scales. Enterprise SOCs that rely on automated objdump-based triage are the most at risk. There is no lateral movement, no data exfiltration, and no privilege escalation.

Detection Guidance

Sigma Rule

title: Objdump Hang - Unbounded Warning Loop
id: 3f7d9c2a-4b31-4e8e-9a0d-c1f2d3e4f5a6
status: experimental
description: Detects a process running objdump that emits the same warning message repeatedly, indicating CVE-2025-69646 exploitation (malformed DWARF debug_rnglists).
author: Valters IT Threat Intelligence
logsource:
  category: process_creation
  product: linux
detection:
  selection:
    Image|endswith: '/objdump'
    CommandLine|contains|all:
      - 'objdump'
  filter_normal:
    CommandLine|contains|any:
      - '--help'
      - '--version'
  condition: selection and not filter_normal
  timeframe: 1s
level: medium
falsepositives:
  - Legitimate repeated objdump invocations in a tight loop (unlikely)
  - Scripts that intentionally run objdump multiple times rapidly

Note: The most effective detection is at the process-output level—a rate-based alert on repeated identical stderr lines. The Sigma rule above targets process creation as a starting point; combine with the Elastic rule below for a more robust detection.

YARA Rule

rule CVE_2025_69646_Malformed_DWARF_Rnglists
{
    meta:
        author = "Valters IT Threat Intelligence"
        description = "Detects ELF binaries with a crafted DWARF5 .debug_rnglists section designed to trigger CVE-2025-69646 in objdump"
        reference = "CVE-2025-69646"
        date = "2025-06-10"
        severity = "medium"
    strings:
        // DWARF 5 version 5 in .debug_rnglists
        $version5 = { 05 00 }                    // version = 5 (DWARF5)
        // DW_RLE_offset_pair encoding (0x04) followed by ULEB128 x=0
        $offset_pair_zero = { 04 00 00 }         // encoding=0x04, x=0, y=0 (identical offsets)
        // unit_length field with all-0xFF bytes (large length causing over-read)
        $huge_length = { FF FF FF FF }
        // Section name string
        $sec_name = ".debug_rnglists"
    condition:
        $sec_name and $version5 and ($offset_pair_zero or $huge_length)
}

Suricata IDS Rule

This vulnerability is exploited via a local file, not a network protocol. However, a Suricata rule can detect the delivery of the malicious binary over common file-transfer channels (HTTP upload, SMB share, email attachment) by inspecting the file content when inline or via a file-extraction script:

alert http any any -> any any (msg:"CVE-2025-69646 - Malformed DWARF debug_rnglists ELF download (potential objdump DoS)"; flow:to_client,established; file.name: /.bin$/; file.data; content:".debug_rnglists"; distance:0; content:"|05 00|"; distance:0; content:"|04 00 00|"; distance:0; classtype:attempted-dos; sid:2025696461; rev:1;)

Note: This rule requires Suricata's file-data inspection (set up with a file-extraction rule) and will generate false positives if legitimate DWARF5 binaries use DW_RLE_offset_pair with equal offsets (which does occur in valid code when a range has zero length). Use in an alert-only mode initially.

Elastic Detection

// EQL to detect a single objdump process emitting high-volume repeated warnings
process where event.action == "start" and process.name == "objdump"
| scan {
    by process.entity_id
    // Count stderr writes over a 10-second window
    // Requires a custom ingest pipeline to parse stderr events
    // Placeholder for log-based correlation:
}

More practical approach (using auditd + systemd journal data ingested into Elastic):

// Detect high-frequency identical warning messages from objdump
sequence by process.entity_id
  [ process where process.name == "objdump" ]
  [ event.category == "process" and process.name == "objdump" ]
  | filter event.duration > 30000 and process.parent.executable != "/usr/bin/make"

Note: The most reliable Elastic detection is a custom watcher that counts log events with the same "process.name: objdump" and the same "message" field appearing more than 100 times within a 60-second window.

Splunk SPL Query

index=linux_os sourcetype=syslog OR sourcetype=journald
| spath input=message path=process.name
| search process.name=objdump
| transaction process_id maxpause=5s
| eval event_count = mvcount(_raw)
| where event_count > 100
| table _time, host, process_id, command, event_count
| sort - event_count

Alternative (if using a custom syslog parser that captures stderr separately):

index=syslog "objdump" "invalid" OR "warning" 
| bucket span=10s _time
| stats count as msg_count by _time, host, source
| where msg_count > 50
| table _time, host, source, msg_count

Wazuh OSSEC Rule

<group name="linux,binutils,denial_of_service,">
  <!-- Detect objdump process looping with repeated warnings -->
  <rule id="100501" level="8">
    <if_sid>100500</if_sid>
    <field name="command" type="pcre">.*objdump.*</field>
    <description>objdump detected running - potential CVE-2025-69646 exploitation</description>
    <group>objdump_dos,</group>
  </rule>

  <!-- Auditd rule for execve of objdump -->
  <rule id="100502" level="6">
    <auditd/>
    <program>auditd</program>
    <action type="execute">execve</action>
    <args type="pcre">.*objdump.*</args>
    <description>objdump executed - monitor for DoS loop</description>
    <group>objdump_dos,</group>
  </rule>

  <!-- Journald message-rate anomaly (requires Wazuh logcollector with multi-line parsing) -->
  <rule id="100503" level="12" frequency="100" timeframes="30">
    <if_matched_sid>100501</if_matched_sid>
    <description>objdump emitted more than 100 same-process messages in 30s - unbounded logging loop confirmed</description>
    <group>objdump_dos,</group>
  </rule>
</group>

Note: For the frequency-based rule to work, Wazuh must be configured to read stderr output from the process or to ingest journald entries that capture the objdump messages.

Mitigation & Patch Guidance

Patch Confidence: 2/4 — CLAIMED — A single source claims a patch exists, but the patch hash or upstream commit has not been independently verified. Treat this as unconfirmed until an official binutils release advisory is published.

1. Immediate Mitigations (no patch yet confirmed):

   • Do not run objdump on untrusted binaries until a patched binutils version is confirmed. Use readelf (readelf -x .debug_rnglists) or LLVM's llvm-objdump (llvm-objdump-18) as a drop-in replacement—they are not affected by this CVE.
   • Apply a Linux timeout wrapper for any automated use of objdump:

     timeout 30s objdump -x "$1" || echo "[!] objdump timed out - possible CVE-2025-69646"
     

     For pipelines, integrate this into the CI runner script.
   • Limit stderr output by redirecting to /dev/null only in controlled environments (but still use the timeout, as CPU exhaustion remains):

     objdump -x "$file" 2>/dev/null
     

   • Isolate analysis in a sandbox with CPU limits (cgroup or taskset -c 0) to prevent a single malicious file from exhausting the entire host.

2. Patch/Upgrade Steps:

   • Monitor the official GNU Binutils repository (git://sourceware.org/git/binutils-gdb.git) and the GNU Binutils mailing list for the release containing the fix. The claimed patch is likely a commit modifying bfd/dwarf2.c or binutils/objdump.c in the debug_rnglists parsing logic.
   • When a patched version is released, upgrade via your distribution's package manager:
     • Debian/Ubuntu: sudo apt update && sudo apt upgrade binutils
     • RHEL/CentOS/Fedora: sudo dnf update binutils
     • Alpine (if used in containers): apk add --upgrade binutils
     • Build from source (for custom toolchains): download the updated tarball from https://ftp.gnu.org/gnu/binutils/ and rebuild.
   • Verify the patch:

     objdump --version  # should show a version > 2.44 with the fix
     # Re-run the crafted binary from the PoC; ensure objdump terminates cleanly:
     objdump -x /tmp/cve-2025-69646-malware.bin
     echo $?  # should return 0 (or a normal error code), not hang
     

3. Long-Term Hardening:

   • Restrict objdump usage via AppArmor/SELinux profiles to only allowed paths; deny execution on downloaded files (/tmp, /var/www/html uploads, /home/*/Downloads) via policy unless explicitly moved to an analysis workspace.
   • Implement CPU and memory limits for all binary-analysis tools using systemd CPUQuota and MemoryMax on custom unit files.
   • Add a log-rate limiter in the logging pipeline (e.g., fail2ban or a custom rsyslog rule) to drop duplicate messages from the same process within a short window.
   • Code review the objdump DWARF parser and submit the fix upstream if you have the resources; the GNU Binutils project is open to contributions.
   • Enable the UNBOUND_YET or malloc protections in the build to reduce secondary memory-exhaustion risks.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2025-69646
2. GNU Binutils Project: https://www.gnu.org/software/binutils/
3. GNU Binutils Source Repository: https://sourceware.org/git/binutils-gdb.git
4. DWARF 5 Debugging Format Specification: https://dwarfstd.org/doc/DWARF5.pdf (for debug_rnglists section layout)
5. CISA Known Exploited Vulnerabilities (KEV) Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog — CVE-2025-69646 is not listed in CISA KEV as of this report's date.

Threat Actor Campaigns: No threat actor campaigns or exploit-in-the-wild evidence have been reported for CVE-2025-69646 as of this writing. The vulnerability is a local DoS, which limits its attractiveness to sophisticated attackers. However, its ease of crafting (a Python script can generate the payload) makes it a credible nuisance threat for targeted denial-of-service against security operations teams.