CVE-2025-52571: Hikka Telegram Userbot Auth Bypass Flaw

CVE-2025-52571 Overview

CVE-2025-52571 is a critical authentication bypass vulnerability affecting Hikka, a popular Telegram userbot framework. This vulnerability allows an unauthenticated attacker to gain full access to a victim's Telegram account as well as complete server compromise. The flaw affects all versions of Hikka below 1.6.2, including most forks of the project that have not applied the security patch.

Critical Impact

Unauthenticated attackers can compromise Telegram accounts and gain full server access without any authentication, potentially exposing sensitive communications and enabling further malicious activities.

Affected Products

• Hikka Telegram userbot versions prior to 1.6.2
• Forks of Hikka that have not incorporated the security patch
• Any deployment running vulnerable versions of the Hikka framework

Discovery Timeline

• 2025-06-24 - CVE-2025-52571 published to NVD
• 2025-06-26 - Last updated in NVD database

Technical Details for CVE-2025-52571

Vulnerability Analysis

This vulnerability is classified under CWE-287 (Improper Authentication), indicating that the Hikka userbot fails to properly validate authentication before granting access to protected functionality. The network-accessible nature of this flaw means attackers can exploit it remotely without any prior authentication, though user interaction is required for successful exploitation.

The vulnerability has a changed scope, meaning successful exploitation affects resources beyond the vulnerable component itself—in this case, both the Telegram account and the underlying server infrastructure. This dual-impact scenario significantly increases the severity, as attackers gain not only access to the victim's messaging platform but also the ability to execute commands on the host system.

Root Cause

The root cause stems from improper authentication mechanisms in versions prior to 1.6.2. The security patch indicates a migration from the telethon library to hikkatl, which includes updated authentication handling. The vulnerable code failed to properly validate user identity before processing requests, allowing unauthorized access to sensitive functionality.

Attack Vector

The attack vector is network-based, requiring some form of user interaction to trigger the vulnerability. Once exploited, an attacker achieves complete compromise of both the Telegram account credentials and full access to the server hosting the Hikka instance. This could enable:

• Theft of Telegram session data and account takeover
• Access to private messages and media
• Remote command execution on the server
• Lateral movement within the network
• Data exfiltration from the compromised system

The security patch in version 1.6.2 includes the following changes to the authentication mechanism:

     print("🚫 Error: you cannot run this as a script; you must execute as a package")
 else:
     try:
-        # If telethon is not installed, just skip to a part of main startup
-        # then main.py will through an error and re-install all deps
-        import telethon
+        import hikkatl
     except Exception:
         pass
     else:
         try:
-            import telethon
+            import hikkatl  # noqa: F811

-            if tuple(map(int, telethon.__version__.split("."))) < (1, 24, 14):
+            if tuple(map(int, hikkatl.__version__.split("."))) < (2, 0, 0):
                 raise ImportError
         except ImportError:
             print("🔄 Installing Hikka-TL...")

Source: GitHub Commit Changes

Detection Methods for CVE-2025-52571

Indicators of Compromise

• Unexpected authentication events or session creation in Telegram accounts linked to Hikka instances
• Unauthorized access attempts to Hikka web interfaces or API endpoints
• Suspicious process execution or network connections originating from Hikka deployment servers
• New or modified files in Hikka installation directories not associated with legitimate updates

Detection Strategies

• Monitor for unauthorized access attempts to Hikka userbot endpoints from external IP addresses
• Implement logging and alerting for authentication events and failures within the Hikka framework
• Review Telegram account activity for unusual login sessions or API token usage
• Audit server access logs for unexpected commands or file modifications in Hikka directories

Monitoring Recommendations

• Enable verbose logging in Hikka deployments to capture authentication attempts and command execution
• Configure network monitoring to detect anomalous outbound connections from Hikka servers
• Implement file integrity monitoring on critical Hikka configuration and binary files
• Set up alerts for new Telegram sessions that do not originate from expected IP ranges

How to Mitigate CVE-2025-52571

Immediate Actions Required

• Upgrade all Hikka installations to version 1.6.2 or later immediately
• Audit existing Telegram sessions connected to Hikka and terminate any suspicious or unrecognized sessions
• Review server access logs for any signs of unauthorized access during the vulnerable period
• If running a fork of Hikka, apply the security patch from commit 9a0e4b1b387ef828c345c43d990421d5afcff5f6

Patch Information

The vulnerability has been addressed in Hikka version 1.6.2. The patch involves migrating from the telethon library to hikkatl with updated authentication validation. The fix can be found in the GitHub Commit. Additional details are available in the GitHub Security Advisory.

Workarounds

• No known workarounds are available for this vulnerability
• The only mitigation is upgrading to version 1.6.2 or applying the security patch
• Consider temporarily taking vulnerable Hikka instances offline until patching is complete
• Restrict network access to Hikka deployments to trusted IP addresses only as a temporary measure

# Upgrade Hikka to patched version
pip install --upgrade hikka>=1.6.2

# Verify installed version
pip show hikka | grep Version

# For fork maintainers, apply the security commit
git cherry-pick 9a0e4b1b387ef828c345c43d990421d5afcff5f6