CVE-2025-2175

Executive Summary

CVE-2025-2175 is a problematic integer overflow vulnerability found in libzvbi up to version 0.2.43. The flaw resides in the _vbi_strndup_iconv function, which can be exploited remotely. An attacker can trigger an integer overflow, potentially leading to memory corruption or denial of service. The exploit has been publicly disclosed, and the vendor has released version 0.2.44 to address the issue. The EPSS score is 0.0%, indicating low exploitation likelihood at this time, but the public PoC increases risk.

Supply Chain & Package Security

This vulnerability affects the libzvbi library, which is a C library for decoding teletext and VBI data. It is not an NPM, PyPI, Go, or Ruby package. However, it may be included as a dependency in various Linux distributions and embedded systems. Users should verify their package manager for updates and ensure libzvbi is upgraded to version 0.2.44 or later.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, but based on the description and public exploit, a more realistic assessment is:

• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: None (C:N)
• Integrity Impact: None (I:N)
• Availability Impact: Low (A:L)
• Base Score: 5.3 (Medium)

The threat level is Medium due to the remote attack vector and public exploit, but low impact on confidentiality and integrity.

Deep Dive & Mechanics

The vulnerability is an integer overflow in the _vbi_strndup_iconv function. This function is used for string duplication with character encoding conversion. When processing a crafted input, the function may miscalculate buffer sizes due to integer overflow, leading to a heap-based buffer overflow. The overflow can corrupt adjacent memory, potentially causing a denial of service or arbitrary code execution.

The attack is launched remotely by sending specially crafted teletext or VBI data to an application using libzvbi. The exploit has been publicly disclosed, meaning attackers can easily replicate it.

Vulnerable vs. Patched Code

The vulnerable code in _vbi_strndup_iconv likely performs a multiplication or addition without overflow checking. For example:

// Vulnerable (version < 0.2.43)
char* _vbi_strndup_iconv(const char* src, size_t n) {
    size_t len = n * 2; // Potential integer overflow
    char* dst = malloc(len);
    // ... conversion logic
}

The patched version (0.2.44) adds overflow checks:

// Patched (version 0.2.44)
char* _vbi_strndup_iconv(const char* src, size_t n) {
    if (n > SIZE_MAX / 2) return NULL; // Overflow check
    size_t len = n * 2;
    char* dst = malloc(len);
    // ... conversion logic
}

Exploitation & Lab Setup

Red Team

1. Setup: Use a vulnerable system with libzvbi 0.2.43 or earlier. Install a tool that processes VBI data (e.g., zvbi-ntsc-cc).
2. Exploit: Send a crafted VBI packet with a large length field to trigger the integer overflow. The public PoC can be used.
3. Payload: The overflow can corrupt heap metadata, leading to a crash or potential code execution.

Example exploit command (hypothetical):

python3 exploit.py --target 192.168.1.100 --port 1234

Blue Team

1. Detection: Monitor for unusual VBI data streams or crashes in applications using libzvbi.
2. Honeypot: Deploy a honeypot running a vulnerable version to capture exploit attempts.
3. Mitigation: Apply the patch or use network segmentation to limit exposure.

Indicators of Compromise (IOCs)

• Network: Unusually large VBI packets or malformed teletext data.
• Host: Crashes in processes using libzvbi (e.g., zvbi-ntsc-cc).
• Memory: Heap corruption patterns in logs or core dumps.
• File: Presence of exploit scripts or binaries targeting libzvbi.

Detection Engineering

YARA Rule

rule CVE_2025_2175_libzvbi {
    meta:
        description = "Detects exploitation attempts of CVE-2025-2175 in libzvbi"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-2175"
    strings:
        $s1 = "_vbi_strndup_iconv" ascii wide nocase
        $s2 = "libzvbi" ascii wide nocase
    condition:
        $s1 or $s2
}

Sigma Rule

title: CVE-2025-2175 Exploitation Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential exploitation of CVE-2025-2175 via malformed VBI data
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/zvbi-ntsc-cc'
        CommandLine|contains: '--input'
    condition: selection
falsepositives:
    - Legitimate VBI processing
level: medium

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2025-2175 libzvbi Integer Overflow Attempt"; flow:to_server; content:"|00 00 00 00|"; depth:4; offset:0; content:"|ff ff ff ff|"; within:4; reference:cve,2025-2175; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Upgrade libzvbi to version 0.2.44 or later.
2. Workaround: If upgrade is not possible, restrict network access to applications using libzvbi.
3. Monitoring: Enable logging for VBI processing and monitor for crashes.
4. Patch Management: Ensure all systems using libzvbi are updated.

Valters IT
DevSecOps & Cyber Threat Intelligence