CVE-2025-49458

Executive Summary

CVE-2025-49458 is a buffer overflow vulnerability in Zoom Workplace Clients that allows an authenticated user to cause a denial of service (DoS) via network access. The vulnerability has a CVSS score of 6.5 (Medium severity) and is currently unpatched. The EPSS score is 0.0%, indicating low exploitation probability in the wild. No public proof-of-concept (PoC) or exploit code is available at this time. The vulnerability affects the Zoom Workplace Client application, potentially impacting enterprise users who rely on Zoom for communication and collaboration.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a native application vulnerability in Zoom Workplace Clients.

CVSS Breakdown & Threat Level

• CVSS Score: 6.5 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: Low (PR:L)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: None (C:N)
• Integrity Impact: None (I:N)
• Availability Impact: High (A:H)

The threat level is considered Medium due to the requirement for authentication and the impact being limited to denial of service. However, the low attack complexity and network attack vector make it a potential risk for enterprise environments.

Deep Dive & Mechanics

The vulnerability is a classic buffer overflow in the Zoom Workplace Client. An authenticated attacker can send specially crafted network packets to the vulnerable client, causing a buffer overflow that leads to a crash or denial of service. The exact vulnerable component is not specified, but it likely involves parsing of network messages or data structures.

The buffer overflow occurs when the client attempts to write data beyond the allocated buffer size, corrupting adjacent memory and causing the application to terminate unexpectedly. This can be exploited repeatedly to disrupt service availability.

Vulnerable vs. Patched Code

Since no patch is available, a direct code comparison cannot be provided. However, the vulnerability likely exists in the network message handling code. A patched version would include bounds checking and input validation to prevent buffer overflows.

Vulnerable Code (Hypothetical):

void process_message(char *data, int len) {
    char buffer[256];
    memcpy(buffer, data, len); // No bounds check
}

Patched Code (Hypothetical):

void process_message(char *data, int len) {
    char buffer[256];
    if (len > sizeof(buffer)) {
        // Handle error
        return;
    }
    memcpy(buffer, data, len);
}

Exploitation & Lab Setup

Red Team

Since no public exploit code is available, a red team would need to reverse-engineer the Zoom Workplace Client to identify the vulnerable function and craft a proof-of-concept. The following steps outline a potential approach:

1. Setup: Install Zoom Workplace Client in a controlled lab environment.
2. Fuzzing: Use a network fuzzer (e.g., Boofuzz) to send malformed packets to the client and monitor for crashes.
3. Crash Analysis: Analyze crash dumps to identify the vulnerable code path.
4. Exploit Development: Develop a buffer overflow payload that triggers a controlled crash.

Example Fuzzing Script (Python):

from boofuzz import *

def test_zoom():
    session = Session(
        target=Target(
            connection=SocketConnection("127.0.0.1", 8800, proto="tcp")
        )
    )
    s_initialize("message")
    s_string("A" * 1000)
    session.connect(s_get("message"))
    session.fuzz()

if __name__ == "__main__":
    test_zoom()

Blue Team

Blue teams should monitor for anomalous network traffic to Zoom Workplace Clients and implement detection rules.

Detection Strategy:

• Monitor for crashes or unexpected terminations of Zoom Workplace Client processes.
• Analyze network traffic for malformed packets targeting Zoom ports.
• Use endpoint detection and response (EDR) tools to detect buffer overflow attempts.

Indicators of Compromise (IOCs)

• Network: Unusually large or malformed packets directed to Zoom Workplace Client ports (e.g., TCP 8800, UDP 3478).
• Host: Crash dumps or logs indicating buffer overflow errors in Zoom Workplace Client.
• Process: Unexpected termination of Zoom.exe or Zoom Workplace process.

Example IOC (YAML):

iocs:
  - type: network
    value: "malformed packets to port 8800"
  - type: process
    value: "Zoom.exe crash"
  - type: log
    value: "Buffer overflow detected in Zoom Workplace Client"

Detection Engineering

YARA Rule

rule CVE_2025_49458_Zoom_Buffer_Overflow {
    meta:
        description = "Detects buffer overflow attempts in Zoom Workplace Client"
        author = "Valters IT"
        date = "2025-01-01"
        cve = "CVE-2025-49458"
    strings:
        $s1 = "Zoom Workplace" ascii wide nocase
        $s2 = "buffer overflow" ascii wide nocase
        $s3 = "crash" ascii wide nocase
    condition:
        any of them
}

Sigma Rule

title: Zoom Workplace Client Buffer Overflow Detection
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential buffer overflow attempts against Zoom Workplace Client
author: Valters IT
date: 2025/01/01
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\\Zoom.exe'
        CommandLine|contains: 'crash'
    condition: selection
falsepositives:
    - Legitimate crashes due to other reasons
level: medium

Suricata Rule

alert tcp any any -> any 8800 (msg:"CVE-2025-49458 Zoom Workplace Client Buffer Overflow Attempt"; flow:to_server; content:"|41 41 41 41|"; depth:1000; threshold:type limit, track by_src, count 1, seconds 60; sid:1000001; rev:1;)

Remediation & Mitigation

Since no patch is available, the following mitigations are recommended:

1. Network Segmentation: Restrict network access to Zoom Workplace Clients to trusted users only.
2. Application Whitelisting: Allow only authorized Zoom versions to run.
3. Monitoring: Implement detection rules (YARA, Sigma, Suricata) to identify exploitation attempts.
4. User Education: Train users to report unusual application behavior.
5. Vendor Communication: Contact Zoom for patch status and workarounds.

Valters IT
Securing Digital Frontiers