CVE-2017-6308 in tnef
Summary
by MITRE
An issue was discovered in tnef before 1.4.13. Several Integer Overflows, which can lead to Heap Overflows, have been identified in the functions that wrap memory allocation.
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Analysis
by VulDB Data Team • 08/17/2020
The vulnerability identified in CVE-2017-6308 affects the tnef library version 1.4.12 and earlier, representing a critical security flaw that stems from improper integer handling during memory allocation operations. This issue manifests as multiple integer overflows within functions responsible for wrapping memory allocation, creating conditions where attackers can manipulate input values to cause unexpected behavior in memory management routines. The vulnerability exists in the core memory allocation logic where integer values are used to determine buffer sizes, and when these integers exceed their maximum representable values, they wrap around to negative or extremely large values, leading to insufficient memory allocation or heap corruption.
The technical flaw specifically occurs when the tnef library processes malformed or specially crafted input data that contains oversized size fields or count parameters. These parameters are used directly in memory allocation functions without proper validation or overflow checking, creating a pathway for attackers to trigger heap overflows through controlled input manipulation. The integer overflow conditions arise from arithmetic operations involving unsigned integers that exceed their maximum bounds, causing the resulting values to wrap around and produce unexpected memory allocation sizes. This vulnerability is classified under CWE-190 as "Integer Overflow or Wraparound" and represents a direct pathway to memory corruption that can be exploited for arbitrary code execution or denial of service conditions.
The operational impact of this vulnerability extends beyond simple memory corruption, as it creates opportunities for attackers to manipulate heap memory layout and potentially execute malicious code within the context of the affected application. When heap overflows occur due to integer overflows in memory allocation functions, they can lead to memory corruption that may be exploited through various attack vectors including stack smashing, heap spraying, or memory pointer manipulation techniques. Applications that utilize the vulnerable tnef library for processing email attachments or other data streams become susceptible to remote code execution if they process untrusted input without proper validation. The vulnerability is particularly concerning because it can be triggered through standard email processing workflows where tnef data is parsed to extract embedded content from winmail.dat files commonly associated with microsoft exchange server communications.
Mitigation strategies for CVE-2017-6308 primarily focus on updating to version 1.4.13 or later of the tnef library where the integer overflow conditions have been addressed through proper input validation and overflow checking mechanisms. Security practitioners should implement comprehensive input validation for all data processed through tnef parsing functions, ensuring that size parameters and count values are properly bounded before being used in memory allocation operations. The fix typically involves adding explicit checks to verify that integer values remain within expected ranges and implementing proper error handling for cases where overflow conditions are detected. Additionally, deployment of application-level sandboxing, memory protection mechanisms, and runtime monitoring can provide additional defense-in-depth measures to detect and prevent exploitation attempts. Organizations should also consider implementing network-based intrusion detection systems that can identify malformed tnef data streams and block suspicious traffic patterns that may indicate exploitation attempts. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter and T1203 for exploitation for execution, as successful exploitation could enable attackers to execute arbitrary code through heap corruption techniques.