CVE-2018-6349 in WhatsApp
Summary
by MITRE
When receiving calls using WhatsApp for Android, a missing size check when parsing a sender-provided packet allowed for a stack-based overflow. This issue affects WhatsApp for Android prior to 2.18.248 and WhatsApp Business for Android prior to 2.18.132.
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Analysis
by VulDB Data Team • 09/03/2025
The vulnerability identified as CVE-2018-6349 represents a critical stack-based buffer overflow flaw in WhatsApp for Android applications that occurred during the processing of incoming calls. This issue emerged from insufficient input validation mechanisms within the application's packet parsing logic, specifically when handling data transmitted by remote senders. The flaw manifested in the absence of proper size verification checks before memory allocation, creating an exploitable condition that could be triggered through maliciously crafted incoming call packets. The vulnerability affected widely distributed applications including standard WhatsApp for Android versions prior to 2.18.248 and WhatsApp Business for Android versions prior to 2.18.132, exposing millions of users to potential exploitation.
The technical implementation of this vulnerability falls under the CWE-121 category of Stack-based Buffer Overflow, where insufficient bounds checking allows attackers to write beyond allocated memory boundaries on the stack. When WhatsApp received incoming calls, the application would parse incoming packets without validating the size of the data received from remote parties, creating a scenario where attacker-controlled data could overwrite adjacent stack memory locations. This type of vulnerability enables attackers to potentially execute arbitrary code on affected devices, as the overflow could overwrite return addresses, function pointers, or other critical stack data structures. The attack vector specifically targeted the application's call handling mechanism, making it particularly dangerous as users could be compromised simply by receiving calls from malicious actors.
The operational impact of this vulnerability extends beyond simple denial-of-service conditions, as it could enable full system compromise through remote code execution. Attackers exploiting this flaw could gain unauthorized access to affected devices, potentially accessing sensitive user data, intercepting communications, or installing additional malware. The widespread adoption of WhatsApp across global markets meant that this vulnerability had significant potential for mass exploitation, particularly in environments where users might receive calls from unknown or untrusted sources. The vulnerability's presence in both standard WhatsApp and WhatsApp Business applications amplified its threat surface, as business users who might have more sensitive communications were equally at risk.
Mitigation strategies for CVE-2018-6349 centered on immediate software updates and patches provided by WhatsApp developers to address the underlying buffer overflow condition. Users were strongly advised to upgrade to the affected versions mentioned in the advisory, specifically 2.18.248 for standard WhatsApp and 2.18.132 for WhatsApp Business, which contained fixed implementations with proper input validation and size checking mechanisms. Network-level defenses could include monitoring for suspicious call patterns or packet structures that might indicate exploitation attempts, though such measures were secondary to the primary requirement for software patching. Organizations implementing security controls should have enforced mandatory application updates and considered network segmentation to limit potential exploitation scope. The vulnerability also highlighted the importance of secure coding practices and input validation in mobile applications, particularly those handling real-time communication data. This incident contributed to broader industry awareness regarding the security implications of mobile messaging platforms and the necessity of robust memory safety mechanisms in client applications.