CVE-2016-2851 in libotr
Summary
by MITRE
Integer overflow in proto.c in libotr before 4.1.1 on 64-bit platforms allows remote attackers to cause a denial of service (memory corruption and application crash) or execute arbitrary code via a series of large OTR messages, which triggers a heap-based buffer overflow.
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Analysis
by VulDB Data Team • 10/09/2024
The vulnerability identified as CVE-2016-2851 represents a critical integer overflow flaw within the Off-the-Record Messaging library version 4.1.0 and earlier, specifically affecting 64-bit systems. This issue resides in the proto.c file component of libotr, which is widely utilized for implementing secure instant messaging protocols. The flaw stems from inadequate input validation when processing OTR messages, creating a scenario where malicious actors can craft specially crafted large messages that trigger unexpected behavior in the library's memory management routines. The vulnerability manifests when the library attempts to calculate buffer sizes based on user-supplied data without proper bounds checking, leading to scenarios where integer arithmetic produces values that exceed the maximum representable integer, causing the system to interpret these values incorrectly in memory allocation contexts.
The technical exploitation of this vulnerability occurs through a carefully constructed sequence of OTR messages that contain oversized data fields, specifically targeting the integer overflow condition in the message processing logic. When the library processes these malformed messages, the overflow causes heap memory corruption by allocating insufficient buffer space or by calculating incorrect buffer boundaries. This memory corruption can result in application crashes due to segmentation faults or more dangerously, enable arbitrary code execution through controlled memory overwrite techniques. The attack vector is particularly dangerous because it requires no authentication or privilege escalation, making it accessible to remote attackers who can simply send malicious OTR messages to vulnerable applications. The vulnerability affects all applications that rely on libotr 4.1.0 or earlier versions for secure messaging, including various instant messaging clients, chat applications, and communication platforms that implement OTR encryption.
The operational impact of CVE-2016-2851 extends beyond simple denial of service conditions, as the vulnerability can potentially be leveraged for complete system compromise. When exploited successfully, the heap-based buffer overflow allows attackers to manipulate memory layout and potentially inject or redirect execution flow within the affected applications. This vulnerability directly maps to CWE-190, which describes integer overflow and underflow conditions, and aligns with ATT&CK technique T1059 for command and scripting interpreter usage, as attackers may attempt to execute arbitrary code through the corrupted memory state. The vulnerability affects the integrity and availability of secure communication channels, potentially enabling man-in-the-middle attacks where attackers can disrupt secure messaging or gain unauthorized access to communication sessions. Organizations using vulnerable versions of libotr face significant risks to their secure communication infrastructure, as the flaw can be exploited to undermine the security guarantees that OTR protocols are designed to provide.
Mitigation strategies for CVE-2016-2851 primarily involve immediate upgrade to libotr version 4.1.1 or later, which includes proper integer overflow protections and bounds checking mechanisms. System administrators should conduct comprehensive inventory assessments to identify all applications utilizing vulnerable libotr versions and implement patch management procedures to ensure timely remediation. Additional defensive measures include implementing network-level filtering to monitor and potentially block suspicious OTR message patterns, though this approach provides limited protection as the vulnerability exists within the library itself. The fix implemented in version 4.1.1 addresses the root cause by introducing proper integer overflow detection and handling routines, ensuring that message size calculations are validated before memory allocation occurs. Security teams should also consider implementing runtime monitoring and anomaly detection systems to identify potential exploitation attempts, as the vulnerability can be difficult to detect through traditional security scanning methods due to its reliance on specific message construction patterns that may not trigger immediate alerts.