CVE-2017-2819 in Thinkfree Office NEO
Summary
by MITRE
An exploitable heap-based buffer overflow exists in the Hangul Word Processor component (version 9.6.1.4350) of Hancom Thinkfree Office NEO 9.6.1.4902. A specially crafted document stream can cause an integer underflow resulting in a buffer overflow which can lead to code execution under the context of the application. An attacker can entice a user to open up a document in order to trigger this vulnerability.
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Analysis
by VulDB Data Team • 12/07/2022
The vulnerability identified as CVE-2017-2819 represents a critical heap-based buffer overflow within the Hangul Word Processor component of Hancom Thinkfree Office NEO version 9.6.1.4350. This flaw resides in the document processing engine responsible for handling various file formats and stream data. The vulnerability stems from inadequate input validation and improper handling of integer values during document parsing operations. Security researchers have classified this issue as a heap-based buffer overflow due to the nature of memory corruption occurring in heap-allocated memory regions during processing of malformed input data. The specific component affected is the Hangul Word Processor which handles Korean text processing and document rendering within the broader office suite framework.
The technical exploitation mechanism involves an integer underflow condition that occurs when processing specially crafted document streams. This underflow results in a calculation error where an integer value becomes unexpectedly small or negative, leading to improper memory allocation decisions. When the application attempts to allocate memory based on this corrupted integer value, it creates a buffer that is insufficiently sized to accommodate the actual data being processed. The resulting buffer overflow allows attackers to overwrite adjacent memory locations, potentially corrupting program execution flow and enabling arbitrary code execution. This vulnerability follows the CWE-121 heap-based buffer overflow pattern where insufficient bounds checking leads to memory corruption. The integer underflow specifically relates to CWE-191 integer underflow conditions that can cause subsequent buffer overflow scenarios.
The operational impact of this vulnerability extends beyond simple code execution as it provides attackers with a potential path to full system compromise. When a user opens a maliciously crafted document, the vulnerability can be triggered without requiring any additional user interaction beyond the normal document opening process. The execution context remains within the application's privileges, meaning successful exploitation could allow attackers to execute arbitrary code with the same permissions as the Thinkfree Office application. This creates a significant risk for enterprise environments where users may inadvertently open compromised documents, potentially leading to data breaches, privilege escalation, or persistent backdoor installations. The vulnerability's exploitation requires minimal user interaction, making it particularly dangerous in phishing scenarios or when documents are shared through untrusted channels. The ATT&CK framework categorizes this as a privilege escalation technique through application execution, where the initial compromise leads to elevated system access.
Mitigation strategies for CVE-2017-2819 should focus on immediate patch application and defensive measures. Organizations should prioritize updating to the latest version of Hancom Thinkfree Office NEO that contains fixes for this vulnerability, as the vendor has likely released a security patch addressing the integer underflow condition. Network-based defenses should include document filtering mechanisms that scan for suspicious file patterns or known malicious indicators within document streams. Email security solutions should implement strict content filtering for office document formats to prevent automatic execution of potentially malicious content. System administrators should consider implementing application whitelisting policies that restrict execution of untrusted office documents, particularly those from unknown sources. Additionally, user education programs should emphasize the importance of avoiding opening documents from untrusted sources and verifying document authenticity before processing. Memory protection mechanisms such as address space layout randomization and data execution prevention should be enabled to reduce the effectiveness of exploitation attempts. The vulnerability highlights the importance of proper integer overflow checking and bounds validation in document processing libraries, particularly in applications handling untrusted input data.