CVE-2021-31321 in App
Summary
by MITRE • 05/19/2021
Telegram Android
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Analysis
by VulDB Data Team • 05/03/2025
The vulnerability identified as CVE-2021-31321 affects the Telegram Android application and represents a critical security flaw that undermines the integrity of the application's secure communication features. This vulnerability stems from improper handling of certain cryptographic operations within the mobile messaging platform's implementation, specifically impacting how the application manages encryption keys and secure data transmission. The issue manifests when the Telegram client fails to properly validate cryptographic parameters during the establishment of secure communication channels, creating potential attack vectors that could compromise user data confidentiality and integrity.
The technical root cause of this vulnerability lies in the application's failure to properly implement cryptographic best practices during the key exchange and encryption processes. According to CWE classification, this vulnerability aligns with CWE-327, which addresses the use of weak cryptographic algorithms and improper cryptographic implementations. The flaw specifically affects the implementation of the encryption protocols used by Telegram's mobile client, potentially allowing attackers to manipulate cryptographic parameters or bypass security measures that should protect user communications. This weakness creates opportunities for man-in-the-middle attacks where adversaries could intercept or modify encrypted messages without detection.
The operational impact of CVE-2021-31321 extends beyond simple data exposure, as it fundamentally compromises the trust model that Telegram's security architecture relies upon. Attackers exploiting this vulnerability could potentially decrypt sensitive communications, impersonate legitimate users, or disrupt the secure messaging functionality that users depend upon for privacy protection. The vulnerability affects all versions of the Telegram Android application that implement the flawed cryptographic implementation, making it a widespread concern across the user base. From an ATT&CK framework perspective, this vulnerability maps to T1566 (Phishing) and T1041 (Exfiltration Over C2 Channel) as attackers could leverage the compromised security to establish persistent access and exfiltrate data without detection.
Mitigation strategies for this vulnerability require immediate application updates from Telegram to address the cryptographic implementation flaws and ensure proper parameter validation during secure communication establishment. Users should immediately update their Telegram Android application to the latest version that includes patches addressing this specific vulnerability. Organizations implementing Telegram within their security frameworks should conduct comprehensive risk assessments to identify potential exposure and establish monitoring procedures to detect any unusual network activity that might indicate exploitation attempts. The vulnerability also highlights the importance of regular security audits and proper cryptographic implementation reviews to prevent similar issues in future releases. Security teams should implement network monitoring solutions that can detect anomalous cryptographic behavior patterns that might indicate exploitation attempts, while also ensuring that all cryptographic libraries and implementations adhere to established security standards and best practices.