ATOK screen lock bypass vulnerability


ATOK from JustSystems Corporation contains a screen lock bypass vulnerability.

ATOK from JustSystems Corporation is a software for Japanese Kana-Kanji conversion. ATOK contains an issue with the restriction of launching external applications, which may lead to a screen lock bypass vulnerability.

Taku Kudo of Google Inc. reported this vulnerability to IPA.
JPCERT/CC coordinated with the developer under Information Security Early Warning Partnership.
CVSS Severity (What is CVSS?)

Base Metrics: 7.2 (High) [IPA Score]
  • Access Vector: Local
  • Access Complexity: Low
  • Authentication: None
  • Confidentiality Impact: Complete
  • Integrity Impact: Complete
  • Availability Impact: Complete

Affected Products

JustSystems Corporation
  • ATOK (For more information, refer to the vendor's website)
  • ATOK smile (For more information, refer to the vendor's website)


An attacker could execute arbitrary code or program with the privileges of the LocalSystem account.

[Update the Software]
Apply the applicable update according to the information provided by JustSystems.
Vendor Information

JustSystems Corporation
CWE (What is CWE?)

  1. Permissions(CWE-264) [IPA Evaluation]
CVE (What is CVE?)

  1. CVE-2009-4738

  1. JVN : JVN#57040664
  2. National Vulnerability Database (NVD) : CVE-2009-4738
  3. IPA SECURITY ALERTS : Security Alert for Vulnerability in ATOK
Revision History

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