A security vulnerability in Telegram Desktop demonstrated how a seemingly harmless link could lead to local file theft and potentially account takeover.
The vulnerability, documented by BeakSec, combines command injection with an internal file-handling feature that lacked proper authorization checks. The result was a chain that could allow an attacker to steal sensitive local files, including Telegram session data.
Original research: BeakSec — Telegram Desktop: One-Click Account Takeover via IPC Injection
What Is the Vulnerability?
According to the original research, the vulnerability affected Telegram Desktop versions through 7.2.8 and was tracked as CVE-2026-107181, with a reported CVSS severity score of 8.1 (High).
The attack combined two security flaws:
- Command injection: Special characters in a crafted link could be interpreted as separators between internal commands.
- Unauthorized file access: An internal Telegram feature could read a local file and send it to a chat without sufficient authorization or user confirmation.
Individually, these flaws were concerning. Combined, they created a potential path from clicking a link to stealing files and compromising a Telegram session.
How Did the Attack Work?
The attack involved several stages.
1. Exploiting Inter-Process Communication (IPC)
Telegram Desktop can already be running when a user clicks a Telegram link. In that situation, a newly launched process can forward the link to the existing application through a local socket.
This communication uses a text-based format in which semicolons separate commands.
The problem was that a semicolon inside the incoming URL was not properly escaped before being passed through this communication channel.
As a result, data intended to represent one URL could be interpreted as multiple internal commands.
This is an example of command injection caused by incorrect input handling across a process boundary.
2. Reaching an Internal File-Handling Feature
The injected command could reach an internal URI scheme called interpret:.
This feature was designed to support Telegram's release-publishing workflow. It could read instructions from a local file and send a specified file to a Telegram channel or group.
However, the feature did not adequately verify whether the request was authorized.
By combining the IPC injection with this functionality, an attacker could potentially cause Telegram Desktop to read files that the attacker should not be able to access.
3. Using Automatically Downloaded Files
The researcher demonstrated how files sent into a Telegram group could be downloaded automatically under certain default settings.
An attacker could prepare instruction files and rely on their predictable download location. A crafted link could then trigger the vulnerable file-handling functionality.
This step made the attack particularly concerning: the victim did not need to manually open the instruction files.
4. Stealing Sensitive Data
Once arbitrary file reading was possible, an attacker could target sensitive information stored locally, including credentials, private keys, configuration files, and Telegram session data.
A stolen session may allow an attacker to impersonate the account owner without needing to know their Telegram password.
The exact impact depends on the files accessible, the application's configuration, and the security protections enabled on the victim's device.
Why Is This Vulnerability Important?
This incident illustrates an important cybersecurity principle: security vulnerabilities often become much more dangerous when combined.
The command injection alone exposed an internal command-processing weakness. The file-handling feature introduced a separate authorization problem.
Together, they created a chain with a potentially serious outcome.
It also highlights several broader lessons for developers:
- Validate and encode input correctly. Data should never be allowed to become executable commands because it contains a delimiter.
- Treat internal features as security-sensitive. A function designed for internal automation can become dangerous if it is reachable through an untrusted input path.
- Apply authorization checks at sensitive operations. Reading and transmitting local files should require appropriate controls.
- Minimize implicit trust. Data received from links, sockets, and downloaded files should be treated as untrusted.
- Review complete attack chains. Fixing one weakness does not necessarily address other weaknesses that an attacker could combine with it.
How Was It Fixed?
According to BeakSec's research, Telegram Desktop 7.2.9 fixed the vulnerability.
The fix removed the legacy interpret: file-sending functionality and introduced proper escaping for the separator used in IPC messages. This prevents a semicolon in a URL from being interpreted as a new command.
The release was published on September 17, 2026, according to the researcher's timeline.
How Can Users Protect Themselves?
If you use Telegram Desktop, take these precautions:
- Update Telegram Desktop. Use version 7.2.9 or later, preferably the latest official release.
- Review automatic download settings. Configure Telegram to ask where to save files instead of automatically downloading them where possible.
- Restrict group invitations. Limit who can add you to groups to reduce exposure to malicious content.
- Set a strong local passcode. This provides an additional layer of protection for local session data, although it does not prevent arbitrary file reads.
- Be cautious with unexpected links. A familiar-looking link is not necessarily safe, particularly when it redirects to another protocol or application.
Updating to a fixed version is the primary defense. The other measures reduce exposure but should not be treated as substitutes for the update.
Final Thoughts
The Telegram Desktop vulnerability is a useful example of how small implementation mistakes can have serious security consequences.
An improperly handled delimiter enabled command injection. An internal feature without adequate authorization made sensitive file access possible. Together, they created a route from a single click to potential account compromise.
For developers, the takeaway is straightforward: never trust input simply because it arrives through an internal interface, and never expose sensitive operations without proper authorization checks.
For users, keeping software updated remains one of the most effective ways to reduce exposure to known vulnerabilities.
Credits and References
This article is based on the original security research by BeakSec:
The original article is published under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. Credit belongs to BeakSec for discovering and documenting the vulnerability. This article is an independently written summary and explanation of that research.
Top comments (1)
tr.ee/dev-to
Some comments have been hidden by the post's author - find out more