Technical Analysis of Telegram Proxy Connection Vulnerability Leading to IP Address Exposure

Problem Identification

What fundamental need does a messaging application serve in terms of user privacy? At its core, it must ensure that communications remain confidential and that users' identities, including their network locations, are protected from unauthorized disclosure. An IP address acts as a digital fingerprint, potentially revealing a user's approximate physical location, internet service provider, and even linking to other online activities.

The specific issue arises: How can a single user interaction within the app compromise this protection, even when safeguards like proxies or VPNs are in place? In the case of Telegram's mobile clients for Android and iOS, clicking a disguised link triggers an unintended network behavior that exposes the user's real IP address to an attacker-controlled server. This occurs without any visible warning, making it a silent and effective vector for targeted surveillance.

Why does this matter? For users in restrictive environments or those relying on anonymity—such as journalists, activists, or individuals evading censorship—this exposure could lead to real-world risks, including tracking, harassment, or worse.

Problem Analysis

To understand the vulnerability, consider the basic mechanics of how Telegram handles proxy connections. Proxies are essential for bypassing network restrictions, but their integration must not create loopholes in privacy.

What causes the exposure? The trigger is a deep link formatted as "tg://proxy?" followed by parameters like server address, port, and secret key. This link can be embedded in a chat message, disguised as a benign username mention (e.g., appearing as @username but hyperlinked to the malicious URI). Upon clicking, the app automatically attempts to verify the proxy's availability before adding it to the configuration.

Why does this bypass existing protections? The verification process—essentially a connection test or ping—occurs outside the app's current proxy or VPN tunnel. Instead of routing through the configured anonymization layer, the app uses the device's direct internet connection. As a result, the request originates from the user's true IP address, which the attacker's server logs immediately.

This behavior stems from a design choice: To prevent users from being locked out if a faulty proxy is added, the app tests new proxies in isolation. However, this isolation inadvertently creates a direct path to the network, undermining the very purpose of proxies.

System Composition

The vulnerability involves Telegram's proxy handling subsystem, which can be broken down into fundamental elements. These are viewed through key concepts and terms:

• Deep Link Handler: A mechanism using custom URI schemes (e.g., tg://) to invoke app-specific actions from external sources like web links or in-app messages. It parses the URI and dispatches to relevant modules.
• Proxy Configuration Module: Responsible for managing proxy settings, including addition, removal, and validation. It interprets parameters like server (IP or domain), port (network endpoint), and secret (authentication key for MTProxy).
• MTProxy Protocol: Telegram's proprietary proxy system, designed for obfuscation and censorship resistance. It uses a lightweight, encrypted tunnel but requires initial connectivity checks.
• Network Interface Layer: Interfaces with the operating system's networking stack (e.g., Android's ConnectivityManager or iOS's URLSession). This layer handles socket creation, DNS resolution, and TCP/UDP connections.
• User Interface Renderer: The chat view component that processes markdown or HTML-like elements, rendering hyperlinks that can mask malicious deep links as innocent text.
• Logging and Error Handling: Internal routines that manage connection failures but do not alert users to potential privacy risks during tests.

Element Interactions and Functional Formation

These elements interact in a sequence to enable proxy management, but their interplay exposes the flaw:

1. The User Interface Renderer displays a message containing a disguised deep link. When the user interacts (clicks), it passes the URI to the Deep Link Handler.
2. The Deep Link Handler extracts parameters (server, port, secret) and forwards them to the Proxy Configuration Module.
3. The Proxy Configuration Module initiates a test using the MTProxy Protocol specifics: It creates a temporary connection attempt via the Network Interface Layer to the specified server and port.
4. Critically, the Network Interface Layer does not apply the current proxy or VPN settings for this test, treating it as a bootstrap operation. This direct connection reveals the real IP to the remote server.
5. If the test succeeds, the proxy might be added; if it fails, an error is logged internally without user notification. The attacker's server, meanwhile, captures the IP independently of the outcome.

This flow forms the proxy addition function but introduces a privacy bypass because the test prioritizes reliability over security. The absence of user consent or routing enforcement allows attackers to exploit the system for IP harvesting without further interaction.

The following diagram illustrates the interaction sequence:

sequenceDiagram
    participant U as User
    participant UI as User Interface Renderer
    participant DL as Deep Link Handler
    participant PM as Proxy Configuration Module
    participant NI as Network Interface Layer
    participant AS as Attacker's Server
    U->>UI: Views message with disguised link
    U->>UI: Clicks link
    UI->>DL: Passes tg://proxy? URI
    DL->>PM: Extracts and sends parameters (server, port, secret)
    PM->>NI: Requests test connection
    NI->>AS: Initiates direct connection (real IP exposed)
    AS->>NI: Responds (success or failure)
    AS-->>AS: Logs real IP
    NI->>PM: Returns test result
    PM-->>DL: Optional: Adds proxy if successful

Note the arrow directions: User actions flow inward to the app, app modules interact sequentially, and the critical exposure occurs in the outward connection from the Network Interface Layer to the attacker's server.

Problem Resolution

How can this exposure be prevented? At the root, the app must ensure that all network operations, including proxy tests, respect the current configuration. Possible solutions include:

• Reroute Tests Through Existing Protections: Modify the Proxy Configuration Module to perform verifications within the active proxy or VPN tunnel, preventing direct IP leakage. If no proxy is set, prompt the user for confirmation.
• User Warnings and Consent: Introduce explicit alerts in the User Interface Renderer when processing proxy links, similar to permissions for camera or location access. This breaks the "one-click" automation.
• Disable Auto-Testing: Shift to manual verification or remove pre-addition pings entirely, relying on user-initiated tests post-configuration.
• Protocol-Level Enhancements: Update the MTProxy Protocol to incorporate anonymized testing, perhaps using onion routing or temporary relays.

For immediate mitigation without app changes: Users should exercise caution with unfamiliar links in chats, even if they appear as mentions. System-level VPNs (rather than app-specific proxies) may offer partial protection if the app's network layer honors them. Additionally, reviewing privacy settings—such as disabling peer-to-peer in calls—can reduce related risks, though it does not directly address this issue.

Ultimately, resolution requires an official update from Telegram to patch the behavior, as no user-configurable option currently exists to block these tests.

References

[1] GangExposed_RU. (2026, January 10). Telegram 1-click vulnerability. X (formerly Twitter). https://x.com/GangExposed_RU/status/2009961303952298348

[2] Cybernews. (2026, January 12). Telegram leaks IP in one click, researchers warn. https://cybernews.com/security/telegram-one-click-vulnerability-leaks-ip-address/

[3] Saurabh. (2026). Telegram 1-click vulnerability verified to reveal your real IP address. LinkedIn. https://www.linkedin.com/posts/saurabh-b294b21aa_telegram-1-click-vulnerability-verified-to-activity-7416116874922393600-4AeP

[4] 0x6rss. (2026, January 10). ONE-CLICK TELEGRAM IP ADDRESS LEAK! X (formerly Twitter). https://x.com/0x6rss/status/2009977902662590787