CVE-2025-1146

Executive Summary

CVE-2025-1146 is a high-severity vulnerability (CVSS 8.1) in CrowdStrike Falcon sensor for Linux, Falcon Kubernetes Admission Controller, and Falcon Container Sensor. The flaw resides in the TLS certificate validation logic, where the sensor incorrectly processes server certificate validation during its connection to the CrowdStrike cloud. This could allow an attacker with network control to perform a man-in-the-middle (MiTM) attack, potentially intercepting or manipulating communications. CrowdStrike identified the issue internally and released a fix in version 7.06 and above. No exploitation in the wild has been observed, and Windows and Mac sensors are not affected.

CVSS Breakdown & Threat Level

• CVSS Score: 8.1 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: High (AC:H) – Requires attacker to control network traffic (e.g., ARP spoofing, DNS poisoning, rogue Wi-Fi).
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H)
• Integrity Impact: High (I:H)
• Availability Impact: High (A:H)

Threat Level: High. While exploitation complexity is high, successful MiTM could lead to full compromise of sensor communications, including exfiltration of sensitive data or injection of malicious commands.

Deep Dive & Mechanics

The vulnerability is a validation logic error in the TLS connection routine of the Falcon sensor. When the sensor establishes a TLS connection to the CrowdStrike cloud, it incorrectly processes server certificate validation. This means the sensor may accept a certificate that does not properly chain to a trusted root CA, or may fail to properly check the certificate's Common Name (CN) or Subject Alternative Name (SAN) against the expected hostname.

An attacker who can intercept network traffic (e.g., via ARP spoofing, DNS poisoning, or rogue Wi-Fi) can present a forged certificate to the sensor. Due to the flawed validation, the sensor would accept this certificate, allowing the attacker to decrypt, read, and modify all traffic between the sensor and the CrowdStrike cloud. This could lead to:

• Theft of API keys, tokens, or other credentials.
• Injection of false telemetry or commands.
• Disruption of sensor functionality.

The fix in version 7.06 corrects the certificate validation logic to ensure proper chain verification and hostname matching.

Vulnerable vs. Patched Code

The vulnerable code is in the TLS connection routine. While the exact source is not public, the logic error likely involves improper use of certificate verification callbacks or incorrect handling of certificate chain validation.

Vulnerable (pre-7.06):

// Pseudocode of flawed validation
if (certificate != NULL) {
    // Incorrectly skips chain validation or hostname check
    connection->valid = 1;
}

Patched (7.06+):

// Pseudocode of corrected validation
if (certificate != NULL && verify_chain(certificate, trusted_store) && verify_hostname(certificate, expected_hostname)) {
    connection->valid = 1;
} else {
    connection->valid = 0;
    close_connection(connection);
}

Exploitation & Lab Setup

Red Team (Attacker)

Prerequisites:

• Ability to intercept network traffic between the Falcon sensor and CrowdStrike cloud (e.g., ARP spoofing on the same subnet, DNS poisoning, or rogue Wi-Fi).
• A machine acting as a MiTM proxy (e.g., using mitmproxy or bettercap).

Steps:

1. Set up a MiTM proxy that intercepts TLS traffic.
2. Generate a self-signed certificate for the CrowdStrike cloud domain (e.g., api.crowdstrike.com).
3. Use ARP spoofing to redirect traffic from the victim sensor to your proxy.
4. When the sensor attempts to connect, the proxy presents the forged certificate.
5. Due to the vulnerability, the sensor accepts the certificate, allowing the attacker to decrypt and modify traffic.

Example using mitmproxy:

# Generate a self-signed certificate for the target domain
openssl req -x509 -newkey rsa:2048 -keyout key.pem -out cert.pem -days 365 -nodes -subj "/CN=api.crowdstrike.com"

# Run mitmproxy with transparent mode
mitmproxy --mode transparent --listen-port 8080 --set block_global=false --certs *=cert.pem

# Use arpspoof to redirect traffic
arpspoof -i eth0 -t <victim_ip> <gateway_ip>

Blue Team (Defender)

Detection:

• Monitor for unexpected TLS certificate errors in sensor logs.
• Look for connections to CrowdStrike cloud from unexpected IPs or with unusual TLS handshake patterns.
• Use network monitoring to detect ARP spoofing or DNS poisoning attempts.

Mitigation:

• Immediately upgrade to Falcon sensor version 7.06 or above.
• Implement network segmentation to limit attacker's ability to intercept traffic.
• Use certificate pinning or additional TLS validation where possible.

Indicators of Compromise (IOCs)

• Network: Unusual TLS handshake failures or certificate warnings from Falcon sensor.
• Logs: Sensor logs showing "certificate validation error" or "untrusted certificate" (pre-patch).
• Process: Unexpected mitmproxy or bettercap processes on the network.
• File: Presence of self-signed certificates for CrowdStrike domains on the network.

Detection Engineering

YARA Rule

rule CVE_2025_1146_TLS_Validation_Error {
    meta:
        description = "Detects Falcon sensor TLS validation error indicators"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-1146"
    strings:
        $s1 = "certificate validation error" nocase
        $s2 = "untrusted certificate" nocase
        $s3 = "TLS handshake failed" nocase
    condition:
        any of them
}

Sigma Rule

title: Falcon Sensor TLS Validation Error
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects TLS validation errors in CrowdStrike Falcon sensor logs
author: Valters IT
date: 2025-04-10
logsource:
    product: linux
    service: falcon-sensor
detection:
    selection:
        EventID: 1001
        Message|contains:
            - 'certificate validation error'
            - 'untrusted certificate'
            - 'TLS handshake failed'
    condition: selection
falsepositives:
    - Legitimate network issues
level: high

Suricata Rule

alert tls $HOME_NET any -> $EXTERNAL_NET 443 (msg:"CVE-2025-1146 - Falcon Sensor TLS Validation Error"; flow:to_server; tls.cert_issuer:!="CrowdStrike"; tls.cert_subject:!="*.crowdstrike.com"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate:

• Upgrade all affected Falcon sensors to version 7.06 or above.
• Verify the upgrade using CrowdStrike Falcon console.

Long-term:

• Implement network segmentation to limit MiTM attack surface.
• Use certificate pinning or additional TLS validation.
• Monitor for any signs of exploitation using the provided detection rules.

Workaround:

• If upgrade is not immediately possible, restrict network access to only trusted gateways and use VPNs to encrypt traffic.

Valters IT