A flaw in the libhangul library causes a null pointer dereference when parsing Hanja dictionary files that contain malformed entries. The library does not validate the presence of a value for a key before dereferencing it, which allows an attacker to supply a specially crafted dictionary file that triggers an unexpected application crash. The crash results in an abrupt termination of the affected process, leading to loss of service for users of the application. The weakness is a classic NULL pointer dereference, classified as CWE-476.

Red Hat Enterprise Linux versions 6, 7, 8, 9, and 10 contain libhangul as part of their standard system libraries. Any application on these platforms that loads the libhangul library when processing Hanja dictionary files is potentially affected. As the issue is present in all these releases, all RH Enterprise Linux installations must verify that their libhangul package is not the vulnerable version.

The CVSS score of 5.5 indicates a medium severity. The EPSS score is not available, and the vulnerability is not listed in CISA’s KEV catalog. Exploitation requires writing a crafted dictionary file that will be read by an application that uses libhangul; this typically implies local access or an application that accepts untrusted file input. Because the flaw fails only with a malformed Hanja file and the attacker can induce a crash but not read or modify memory, the vulnerability presents a limited risk of denial of service only. Red Hat notes that no viable temporary workaround exists or that existing options do not meet their security criteria, so the risk remains moderate until a vendor fix is released.