What is CVE-2023-39731?

CVE-2023-39731 is a medium-severity vulnerability in Line Kaibutsunosato, classified under Improper Access Control. CVSS score: 5.3/10. Published 2023-10-20.

How severe is CVE-2023-39731?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Line Kaibutsunosato

CVE-2023-39731

The leakage of the client secret in Kaibutsunosato v13.6.1 allows attackers to obtain the channel access token and send crafted broadcast messages.

Published 2023-10-20 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.004 (27.5th percentile), scored 2026-10-05.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 28th percentile — 27.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000

Affected products

Line Kaibutsunosato — versions 13.6.1

Weakness classification (CWE)

CWE-284 — Improper Access Control

References

github.com/syz913/CVE-reports/blob/main/CVE-2023-39731.md (Third Party Advisory)
liff.line.me/1657662489-pwEQNzJ4 (Vendor Advisory)

Frequently asked questions

What is CVE-2023-39731?: CVE-2023-39731 is a medium-severity vulnerability in Line Kaibutsunosato, classified under Improper Access Control. CVSS score: 5.3/10. Published 2023-10-20.
How severe is CVE-2023-39731?: Medium severity. CVSS v3 base score is 5.3 out of 10.