CVE-2025-59595

Executive Summary

CVE-2025-59595 is a denial of service (DoS) vulnerability discovered internally in Ivanti Secure Access versions prior to 14.12. An attacker can send a specially crafted packet to a server running a non-default configuration, causing the server to crash. This vulnerability does not require authentication and can be exploited remotely, leading to service disruption. No public proof-of-concept (PoC) or exploit code is available at this time. The vendor has released a fix in version 14.12.

Supply Chain & Package Security

This vulnerability is not related to an open-source package (NPM, PyPI, Go, Ruby). It affects a proprietary Ivanti product. Supply chain risk is limited to the integrity of the Ivanti update process.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, indicating that a full vector has not been assigned by NVD. However, based on the description, the following assessment is made:

• Attack Vector (AV): Network (N) – The attack is performed remotely.
• Attack Complexity (AC): Low (L) – The attack requires a specially crafted packet but no complex conditions.
• Privileges Required (PR): None (N) – No authentication is needed.
• User Interaction (UI): None (N) – No user action is required.
• Scope (S): Unchanged (U) – The vulnerability affects only the vulnerable component.
• Confidentiality (C): None (N) – No data exposure.
• Integrity (I): None (N) – No data modification.
• Availability (A): High (H) – The server crashes, causing a complete loss of availability.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Threat Level: High (Availability impact). The vulnerability is easy to exploit remotely without authentication, making it a significant risk for service continuity.

Deep Dive & Mechanics

The vulnerability resides in the packet processing logic of Ivanti Secure Access. Under a non-default configuration (details not publicly disclosed), the server fails to properly handle a specially crafted network packet. This leads to an unhandled exception or resource exhaustion, causing the server process to crash.

Root Cause: Improper input validation or boundary checking in the packet parsing routine. The non-default configuration likely enables a feature that exposes a vulnerable code path.

Attack Vector: An unauthenticated attacker sends a single or series of crafted packets to the target server. The server crashes, denying service to legitimate users.

Impact: Complete denial of service. The server must be restarted manually or automatically to restore functionality.

Vulnerable vs. Patched Code

No specific code snippets are available. The fix in version 14.12 likely involves:

• Adding input validation for the crafted packet fields.
• Implementing bounds checking to prevent buffer overflows or infinite loops.
• Hardening the packet parsing routine to handle malformed data gracefully.

General Example (Hypothetical):

// Vulnerable code (before fix)
void process_packet(char *data, int len) {
    int field_len = *(int*)data; // No validation
    char buffer[1024];
    memcpy(buffer, data + 4, field_len); // Potential overflow
}

// Patched code (after fix)
void process_packet(char *data, int len) {
    if (len < 4) return;
    int field_len = *(int*)data;
    if (field_len < 0 || field_len > 1020) return; // Validation
    char buffer[1024];
    memcpy(buffer, data + 4, field_len);
}

Exploitation & Lab Setup

Red Team

Objective: Crash the Ivanti Secure Access server.

Prerequisites:

• Target running Ivanti Secure Access < 14.12 with a non-default configuration.
• Network access to the target.

Steps:

1. Identify the target IP and port (typically 443 for SSL VPN).
2. Craft a malicious packet that triggers the vulnerability. Since no public PoC exists, this requires reverse engineering the vulnerable code path.
3. Send the packet using a tool like scapy or a custom Python script.

Example (Hypothetical):

import socket

target_ip = "192.168.1.100"
target_port = 443

# Craft a malformed packet (hypothetical structure)
malformed_packet = b"\x00" * 100  # Placeholder

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((target_ip, target_port))
sock.send(malformed_packet)
sock.close()

Note: Without a public PoC, this is speculative. Actual exploitation requires detailed knowledge of the vulnerable code.

Blue Team

Objective: Detect and prevent exploitation.

Steps:

1. Patch: Upgrade to Ivanti Secure Access 14.12 immediately.
2. Monitor: Look for unusual network traffic patterns, especially malformed packets targeting the VPN service.
3. Harden: Review and disable non-default configurations that may expose the vulnerable code path.
4. IDS/IPS: Deploy signatures to detect the specific packet pattern (once known).

Indicators of Compromise (IOCs)

• Network: Unusual TCP packets with malformed headers or payloads targeting port 443 (or other VPN ports).
• System: Server crash logs, unexpected service restarts, or core dumps.
• Logs: Entries indicating a crash in the Ivanti Secure Access service.

Example Log Entry:

[ERROR] Unhandled exception in packet_handler.c:123. Server shutting down.

Detection Engineering

YARA Rule

rule CVE_2025_59595_Ivanti_DoS {
    meta:
        description = "Detects potential exploit attempts for CVE-2025-59595"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-59595"
    strings:
        $suspicious_packet = { 00 00 00 [4-8] FF FF FF FF } // Hypothetical pattern
    condition:
        $suspicious_packet
}

Sigma Rule

title: Ivanti Secure Access DoS Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects network traffic attempting to exploit CVE-2025-59595
author: Valters IT
date: 2025-04-10
logsource:
    category: network_connection
    product: suricata
detection:
    selection:
        dest_port: 443
        payload|contains: "00 00 00 FF FF FF FF" # Hypothetical
    condition: selection
falsepositives:
    - Legitimate traffic with similar patterns (unlikely)
level: high

Suricata Rule

alert tcp any any -> any 443 (msg:"CVE-2025-59595 Ivanti Secure Access DoS Attempt"; content:"|00 00 00 FF FF FF FF|"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate:

• Upgrade to Ivanti Secure Access version 14.12 or later.
• If upgrade is not possible, disable the non-default configuration that exposes the vulnerability (details from Ivanti advisory).

Long-term:

• Implement network segmentation to limit exposure of VPN servers.
• Deploy intrusion detection/prevention systems (IDS/IPS) with custom signatures.
• Regularly review and apply vendor security patches.
• Conduct internal security assessments and code reviews.

Workaround: None publicly available. The only mitigation is to patch or disable the vulnerable configuration.

Valters IT
Securing Digital Frontiers