CVE-2025-66865

Executive Summary

CVE-2025-66865 is a denial-of-service (DoS) vulnerability in the GNU Binutils library, specifically within the d_print_comp_inner function in the cp-demangle.c file. The flaw is triggered when processing a crafted Portable Executable (PE) file, leading to a crash or hang. The vulnerability affects Binutils version 2.26. No official patch has been released, and no public proof-of-concept (PoC) or exploit code is available at this time. The EPSS score is 0.0%, indicating a very low probability of exploitation in the wild. This is a memory safety issue (likely a NULL pointer dereference or infinite recursion) that can be used by an attacker to disrupt services that rely on Binutils for PE file processing.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder. Based on the description and CWE-476 (NULL Pointer Dereference), a reasonable CVSS v3.1 vector would be:

• Attack Vector (AV): Local (L) – requires the attacker to provide a crafted PE file.
• Attack Complexity (AC): Low (L) – no special conditions.
• Privileges Required (PR): None (N) – no authentication needed.
• User Interaction (UI): Required (R) – victim must process the file.
• Scope (S): Unchanged (U) – only the vulnerable component is affected.
• Confidentiality (C): None (N) – no data leak.
• Integrity (I): None (N) – no data modification.
• Availability (A): High (H) – service crash or hang.

Estimated CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H Estimated Base Score: 5.5 (Medium)

Threat Level: Medium. The vulnerability requires local access and user interaction, but can cause a denial of service. No active exploitation has been observed.

Deep Dive & Mechanics

The vulnerability resides in the d_print_comp_inner function within cp-demangle.c. This function is part of the C++ name demangling routine used by Binutils tools (e.g., objdump, nm, size) when processing object files, including PE files. The function recursively traverses a tree structure representing a mangled name. A crafted PE file can cause the function to enter an infinite recursion or dereference a NULL pointer, leading to a stack overflow or segmentation fault.

Root Cause: The function does not properly validate the depth or structure of the demangling tree. An attacker can craft a PE file with a deeply nested or malformed mangled name that causes the recursive function to exceed stack limits or access invalid memory.

Attack Vector: An attacker delivers a malicious PE file to a victim. When the victim uses a Binutils tool (e.g., objdump -d malicious.exe) to analyze the file, the vulnerable code path is triggered, causing the tool to crash or hang.

Impact: Denial of service. The tool becomes unavailable for legitimate use. In automated environments (e.g., malware analysis sandboxes), this can disrupt operations.

Vulnerable vs. Patched Code

Vulnerable Code (Binutils 2.26, cp-demangle.c): The d_print_comp_inner function lacks depth or recursion guards. A simplified representation:

static void d_print_comp_inner (struct d_print_info *dpi, int options, struct demangle_component *dc) {
    if (dc == NULL) return;
    switch (dc->type) {
        case DEMANGLE_COMPONENT_NAME:
            // ... print name
            break;
        case DEMANGLE_COMPONENT_QUAL_NAME:
            d_print_comp_inner(dpi, options, dc->u.s_binary.left);
            d_print_comp_inner(dpi, options, dc->u.s_binary.right);
            break;
        // ... many other cases
    }
}

Patched Code (Hypothetical): A patch would add a recursion depth counter and a maximum depth limit:

#define MAX_DEMANGLE_DEPTH 1024

static void d_print_comp_inner (struct d_print_info *dpi, int options, struct demangle_component *dc, unsigned int depth) {
    if (dc == NULL) return;
    if (depth > MAX_DEMANGLE_DEPTH) {
        // Error handling: abort or return
        return;
    }
    switch (dc->type) {
        case DEMANGLE_COMPONENT_QUAL_NAME:
            d_print_comp_inner(dpi, options, dc->u.s_binary.left, depth + 1);
            d_print_comp_inner(dpi, options, dc->u.s_binary.right, depth + 1);
            break;
        // ...
    }
}

Note: No official patch has been released. The above is a recommended fix.

Exploitation & Lab Setup

Red Team

Objective: Cause a denial of service on a system running Binutils 2.26.

Lab Setup:

1. Environment: Ubuntu 16.04 or any Linux distribution with Binutils 2.26 installed.
2. Tool: objdump (part of Binutils).
3. Crafted PE File: Create a PE file with a deeply nested mangled C++ symbol. This can be done by:
   • Compiling a C++ program with a deeply nested namespace/class structure.
   • Manually editing the PE file's symbol table to include a malformed mangled name.
   • Using a fuzzer (e.g., AFL) to generate a crashing input.

Exploitation Steps:

1. Transfer the crafted PE file to the target system.
2. Execute: objdump -d crafted_pe_file.exe
3. Observe the tool crash (segmentation fault) or hang indefinitely.

Expected Outcome: The objdump process terminates unexpectedly, causing a denial of service for that specific analysis task.

Blue Team

Detection:

• Monitor for crashes of Binutils tools (objdump, nm, size, strings).
• Use process monitoring to detect abnormal termination signals (SIGSEGV, SIGABRT).
• Analyze core dumps to identify the crash location in cp-demangle.c.

Prevention:

• Upgrade to a patched version of Binutils (when available).
• Use a sandboxed environment for processing untrusted PE files.
• Implement resource limits (e.g., ulimit -s to limit stack size) to mitigate stack overflow.

Hunting:

• Search for PE files with unusually long or deeply nested symbol names.
• Correlate crashes of Binutils tools with recent file processing events.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): (No known samples yet)
• Process Names: objdump, nm, size, strings (crashing)
• Error Logs: Segmentation fault in d_print_comp_inner at cp-demangle.c
• Network: None (local vulnerability)
• Registry: None

Detection Engineering

YARA Rule

rule CVE_2025_66865_Binutils_PE_Demangle_DoS {
    meta:
        description = "Detects crafted PE files targeting CVE-2025-66865 in Binutils"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-66865"
        hash = "unknown"
    strings:
        $mangled_pattern = /_Z[A-Za-z0-9_]+/  // Simplified mangled name pattern
        $deep_nesting = /_Z[^ ]{1024,}/        // Very long mangled name (potential trigger)
    condition:
        uint16(0) == 0x5A4D and                // MZ header
        $deep_nesting
}

Sigma Rule

title: Binutils Tool Crash Due to Crafted PE File
id: 7b8c9d0e-1f2a-3b4c-5d6e-7f8a9b0c1d2e
status: experimental
description: Detects crashes of Binutils tools (objdump, nm, size) likely caused by CVE-2025-66865
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith:
            - '/objdump'
            - '/nm'
            - '/size'
            - '/strings'
        ExitCode: -11  # SIGSEGV
    condition: selection
falsepositives:
    - Legitimate crashes due to other bugs
level: medium

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-66865 Potential Binutils DoS via PE File Transfer"; flow:to_server; file_data; content:"MZ"; within:2; content:"|00 00 00 00|"; distance:0; pcre:"/_Z[^ ]{1024,}/"; classtype:attempted-dos; sid:1000001; rev:1;)

Note: The Suricata rule is a heuristic detection for PE files with very long mangled names being transferred over the network. It may generate false positives.

Remediation & Mitigation

Immediate Actions:

1. Isolate: Do not process untrusted PE files with Binutils 2.26.
2. Monitor: Watch for crashes of Binutils tools and investigate the triggering files.
3. Workaround: Use alternative tools (e.g., readelf, llvm-objdump) for PE file analysis.

Long-Term Fix:

• Apply a patch from the Binutils maintainers when available.
• If patching is not possible, apply the code fix described in the "Vulnerable vs. Patched Code" section (add recursion depth limit).
• Upgrade to a newer version of Binutils (e.g., 2.27 or later) that may have addressed this issue.

Detection:

• Deploy the YARA, Sigma, and Suricata rules provided in the Detection Engineering section.
• Enable core dumps and analyze them for crashes in d_print_comp_inner.

Valters IT
DevSecOps & Cyber Threat Intelligence