CVE-2021-36769 in App
Summary
by MITRE • 07/17/2021
A reordering issue exists in Telegram before 7.8.1 for Android, Telegram before 7.8.3 for iOS, and Telegram Desktop before 2.8.8. An attacker can cause the server to receive messages in a different order than they were sent a client.
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Analysis
by VulDB Data Team • 07/19/2021
The vulnerability identified as CVE-2021-36769 represents a significant message ordering issue within the Telegram messaging platform across multiple client implementations. This reordering problem affects Telegram versions prior to 7.8.1 for Android, 7.8.3 for iOS, and 2.8.8 for Desktop platforms, creating a fundamental flaw in the message delivery mechanism that could compromise the integrity of communication sequences. The vulnerability stems from improper handling of message queuing and transmission protocols within the client-side software, where the chronological order of messages is not properly maintained during the transmission process to the Telegram servers.
The technical flaw manifests as a race condition or sequencing issue in the client's message processing pipeline where outbound messages are not consistently sent in the order they were composed or queued. This reordering occurs during the network transmission phase where multiple messages may be batched together or processed concurrently without proper temporal sequencing mechanisms. The issue is particularly concerning because it affects the fundamental communication integrity that users expect from instant messaging platforms, where the order of messages directly impacts the meaning and context of conversations. From a cybersecurity perspective, this vulnerability could enable attackers to manipulate the perceived sequence of communications, potentially leading to confusion, misinterpretation of events, or even exploitation in social engineering attacks.
The operational impact of this vulnerability extends beyond simple message confusion, as it could enable sophisticated attack vectors that leverage the reordered message delivery to create misleading communication sequences. Attackers could potentially exploit this behavior to make users believe messages were sent in a different order than actually occurred, which might be particularly damaging in professional or sensitive communication contexts. The vulnerability aligns with CWE-1244 which describes improper message ordering in distributed systems, and could be categorized under ATT&CK technique T1566 for social engineering attacks that manipulate communication timing. Organizations relying on Telegram for business communications may face risks related to information integrity, audit trails, and potential exploitation in targeted attacks where message sequence manipulation could be used to create false narratives or confuse incident response procedures.
The remediation for this vulnerability requires updating to the patched versions of Telegram clients, specifically version 7.8.1 for Android, 7.8.3 for iOS, and 2.8.8 for Desktop platforms. These updates implement proper message queuing mechanisms that maintain chronological order during transmission, ensuring that messages are delivered to servers in the same sequence they were generated by the client. Security teams should prioritize deployment of these patches across all affected systems and conduct verification testing to confirm that message ordering behavior has been restored. Additionally, organizations should consider implementing monitoring for unusual message delivery patterns that might indicate continued vulnerability exploitation attempts, and should review their incident response procedures to account for potential message reordering effects in communication forensics and analysis.