Telegram rlottie numeric truncation can enable remote code execution

Telegram rlottie Numeric Truncation Remote Code Execution Vulnerability. This vulnerability allows remote attackers to execute arbitrary code on affected installations of Telegram. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file. The specific flaw exists within the rlottie library. The issue results from the lack of proper validation of user-supplied data, which can result in a write before the start of an allocated buffer. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-30207.

• Vendor and product: Telegram, including the rlottie library.
• Version 6.6.2 is marked affected.
• Default status is unknown. The available evidence does not establish additional affected branches or a fixed release.

The flaw is in Telegram's rlottie library and is classified as CWE-197, Numeric Truncation Error. User-controlled data reaches the library's processing logic without adequate validation, which can cause a write before the start of an allocated buffer. Exploitation requires the target to visit a malicious page or open a malicious file so that the content is processed. The record describes remote attackers, while the normalized attack metadata marks the attack vector as local, so the exact delivery model is not fully resolved. The specific data field, parser path, and implementation function involved are not identified in the available evidence.

Exploitation requires user interaction: the target must visit a malicious page or open a malicious file in Telegram. The supplied metadata indicates that no pre-existing privileges are required, attack complexity is high, and scope is unchanged; the attack vector is marked local. ZDI published the case as a 0-day advisory. The record states that there is no public exploit and does not establish known exploitation, but this is not evidence that exploitation has never occurred outside the supplied record.

The flaw can lead to arbitrary code execution in the current Telegram process after malicious content is processed. The technical outcome could affect the confidentiality, integrity, and availability of data or services accessible to that process. The record does not establish privilege escalation, impact across a separate security scope, or access beyond the current process permissions. The practical consequence depends on the process privileges, endpoint configuration, and whether the user performs the required interaction.

Successful exploitation could allow attacker-controlled code to run in the context of the current Telegram process.

• Depending on the process permissions and endpoint environment, consequences could include loss of confidentiality, unauthorized data changes, or service disruption.
• The user-interaction requirement reduces the likelihood of fully automated exploitation, but does not remove the risk from malicious files or pages that users trust and open.
• The record does not provide evidence of a specific breach, victim, or active campaign.

1. Prioritize the vendor's official update when a fixed release is confirmed. The available evidence does not identify a fixed version, so no specific release should be inferred as a fix.
2. Until a fixed release is confirmed, apply the mitigation identified by ZDI: restrict interaction with Telegram, particularly visits to untrusted pages and opening of untrusted files through affected installations.
3. ZDI reports that the vendor stated the vulnerability was mitigated by server-side validation. Do not treat that statement as proof that every content-delivery path or client endpoint has been fixed.
4. Isolate or upgrade Telegram installations running version 6.6.2, and restrict untrusted content processing on installations without a confirmed fix.

1. Inventory Telegram installations and identify systems running version 6.6.2.
2. Identify endpoints where Telegram processes files or content from untrusted sources, especially workflows in which users open files directly.
3. Check vendor update information for a confirmed fixed release; the available evidence does not provide one.
4. Review available endpoint telemetry for abnormal Telegram behavior after a user opens suspicious content. Treat this as precautionary monitoring because no specific IOC or log event has been provided.
5. Do not treat the absence of suspicious log evidence as proof that an installation is safe.