A critical vulnerability was discovered in Telegram Desktop that could allow attackers to steal files from a computer and gain access to other users’ accounts through a single malicious link. To exploit the flaw, an attacker only needs to trick a user into opening a specially crafted URL, after which the messenger could automatically send sensitive data to the attackers.
Cybersecurity researcher BeakSec disclosed details of a Telegram Desktop vulnerability affecting versions prior to 7.2.9. The flaw allows attackers to execute hidden internal commands, access local files, and steal authentication data needed to restore another user’s Telegram session.
The issue was fixed in version 7.2.9, released on September 17, 2026. At the time of publication, version 7.3 was already available, having been released on October 9 with a brief update description consisting of just one word: “Money.”
“Someone adds you to a Telegram group. A link appears in the chat. You click it, and your Telegram account no longer belongs only to you,” BeakSec explains.
The vulnerability stems from improper handling of special characters in links. Telegram Desktop uses semicolons (;) to separate internal commands, but vulnerable versions of the application failed to properly escape this character.
Attackers could exploit the flaw by creating a specially crafted tg:// link containing additional commands after a semicolon. Instead of treating the address as a single link, Telegram could process its components as separate instructions.
The mechanism has certain limitations. The application supports only four types of commands, three of which pose no direct threat. However, the fourth provides access to an internal handler called interpret:, which became the key component of the attack.
This mechanism was originally designed for Telegram’s internal development purposes, including automating the publication of new application releases. It can read a file from the local disk and send it to a specified chat without requiring additional user confirmation.
The problem was that the handler did not verify who initiated the operation. Combined with the link-parsing flaw, this allowed external attackers to invoke privileged functions through a specially crafted URL.
BeakSec demonstrated an attack scenario in which an attacker creates a Telegram supergroup and adds a potential victim. Telegram’s default privacy settings may allow users to be added to groups without their explicit confirmation.
The attacker then posts three specially prepared .txt files in the group. Under Telegram Desktop’s default settings, files up to 8 MiB are automatically downloaded from group chats, meaning they may already be stored on the victim’s computer before the user takes any action.
Next, an ordinary-looking HTTPS link appears in the chat. In reality, it leads to an attacker-controlled server that redirects the user to a specially crafted tg:// URL containing hidden commands.
When the victim clicks the link, the browser processes the redirect, and the operating system may launch a second Telegram process. That process forwards the URL to the already running instance of the messenger, where the delimiter-handling flaw causes additional instructions to be executed.
As a result, Telegram can automatically read the targeted files and send them to a group controlled by the attacker. The application itself does not request confirmation before transferring the files, although the browser may sometimes ask for permission to open an external application.
In the demonstrated attack, the attacker targets three files used to store a local Telegram session. These include an encryption key, authentication data, and an index of stored account information.
Relative file paths are used to locate the necessary files. This means the attacker does not need to know the victim’s Windows username or the exact location of their home directory.
Once the attacker obtains these files, they can transfer them to a new instance of Telegram Desktop and restore the victim’s session. This allows them to access the account without going through the usual phone number login process, provided the user has not set a local passcode for the application.
However, the vulnerability’s capabilities extend beyond stealing Telegram accounts. According to the researcher, the same mechanism could potentially be used to retrieve other files from the computer, including private SSH keys, browser password stores, cloud credentials, and configuration files containing API tokens.
The Telegram Desktop local passcode plays a particularly important role in this scenario. It is not enabled by default, meaning stolen session files could be used to restore access. If the user has configured a strong local passcode, exploiting the stolen data becomes significantly more difficult.
The vulnerability was assigned the identifier CVE-2026-107181. It received a severity score of 8.6 out of 10 under CVSS 4.0, placing it in the high-severity category. Under the earlier CVSS 3.1 scoring system, it received a score of 8.1.
The researcher reported the issue through the Zero Day Initiative (ZDI) on June 25, 2026. However, Telegram independently fixed the vulnerability on September 16 and released version 7.2.9 the following day.
The patch removed the dangerous internal interpret: handler and modified how commands are passed between Telegram processes. Special characters in URLs are now handled more securely, while additional checks prevent suspicious instructions from being executed.
Interestingly, the fix was released without a separate security advisory. The changelog for version 7.2.9 mentioned only a user interface rendering fix, while the corresponding commit had a technical name that gave no indication of a serious security vulnerability.
On September 30, ZDI closed the report because the issue had already been fixed. BeakSec published a technical analysis of the attack on October 3, and the vulnerability was assigned its CVE identifier on October 7.
First and foremost, the researcher recommends updating Telegram Desktop to version 7.2.9 or later. The update fixes the vulnerability itself, while other security measures only reduce the risk of a successful attack.
Users should also restrict who can add them to groups, set a strong local passcode for Telegram Desktop, and enable the “Ask where to save each file” option. This setting disables automatic file downloads, which attackers could otherwise exploit to place prepared instructions on a victim’s computer.
A local passcode does not prevent files from being stolen, but it protects the stored session from being reused on another device. Restricting group invitations also makes the described attack scenario more difficult to carry out.
It is worth noting that the researcher demonstrated the attack on Windows. Telegram Desktop versions prior to 7.2.9 were identified as vulnerable, but this does not mean the same attack scenario was independently confirmed on every operating system.
The Telegram Desktop case demonstrates how flaws in an application’s internal mechanisms can turn an ordinary link into a tool for stealing sensitive files and gaining access to user accounts. The vulnerability has already been fixed, so the most important step for users is to avoid running outdated versions of the messenger.
