CVE-2026-108063 in Red Hat
Summary
by MITRE • 10/09/2026
A flaw was found in libhangul. When parsing Hanja dictionary files, the library fails to verify that an entry contains a valid value alongside its key. By providing a specially crafted dictionary file to an application that queries it, an attacker can trigger an unexpected application crash, resulting in a Denial of Service (DoS).
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Analysis
by VulDB Data Team • 10/09/2026
The vulnerability identified within libhangul represents a critical input validation failure during the processing of Hanja dictionary files. Libhangul is a widely used open-source library responsible for handling Korean character encoding and conversion, including support for Hanja, which are Chinese characters adopted into the Korean language. The core technical flaw lies in the parsing logic that handles these dictionary entries. Specifically, when the library processes an entry, it assumes that every key provided has a corresponding valid value associated with it. However, there is no rigorous verification step to ensure this assumption holds true for all inputs. This lack of defensive programming allows malformed or specially crafted dictionary files containing keys without valid values to bypass internal checks and proceed through the parsing pipeline.
From an operational perspective, this oversight leads directly to a Denial of Service condition when the library encounters such invalid data structures in memory. Because the application relying on libhangul does not anticipate missing value pointers or null references resulting from these malformed entries, it triggers an unexpected crash upon access. This behavior is particularly dangerous because dictionary files are often treated as trusted resources by applications that utilize them for text input and conversion features. An attacker who can persuade a user to open a maliciously crafted Hanja dictionary file can exploit this flaw to cause the host application to terminate abruptly. The impact extends beyond simple instability; it disrupts workflow continuity, potentially leading to data loss if unsaved work is involved, and degrades the overall reliability of software systems that depend on accurate Korean text processing capabilities.
This vulnerability aligns with CWE-20 Improper Input Validation, as the system fails to adequately sanitize or verify user-supplied input before using it in operations that assume specific structural integrity. Furthermore, from a threat modeling perspective consistent with MITRE ATT&CK frameworks, this flaw facilitates availability impact categories such as T1499 Endpoint Denial of Service. The attack vector typically involves social engineering tactics where an adversary distributes the malicious dictionary file through email attachments, compromised websites, or other distribution channels to trick users into opening it within applications that integrate libhangul for text input methods.
Mitigation strategies must focus on both immediate patching and long-term architectural improvements. Developers should immediately update to patched versions of libhangul where this validation logic has been corrected to explicitly check for the existence and validity of values associated with keys before processing them. For organizations unable to apply patches instantly, implementing strict file integrity checks or sandboxing applications that process external dictionary files can reduce the risk of successful exploitation. Additionally, adopting secure coding practices that enforce rigorous input validation at all entry points is essential to prevent similar flaws in future development cycles. Security teams should also monitor for any emerging exploits targeting this specific library and ensure that end-users are educated about the risks associated with opening untrusted document types from unknown sources.