What is CVE-2025-64781?

CVE-2025-64781 is a medium-severity vulnerability in Groupsession, classified under Initialization of a Resource with an Insecure Default. CVSS score: 4.7/10. Published 2025-12-12.

How severe is CVE-2025-64781?

Medium severity. CVSS v3 base score is 4.7 out of 10.

RCE in Groupsession

CVE-2025-64781

In GroupSession Free edition prior to ver5.7.1, GroupSession byCloud prior to ver5.7.1, and GroupSession ZION prior to ver5.7.1, "External page display restriction" is set to "Do not limit" in the initial configuration. With this configuration, the user may be redirected to an arbitrary website when accessing a specially crafted URL.

Published 2025-12-12 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.7 (Medium). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.002 (9.7th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 10th percentile — 9.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000

Affected products

Groupsession
Japan Total System Co.,ltd. Groupsession Bycloud — versions prior to ver5.7.1
Japan Total System Co.,ltd. Groupsession Free Edition — versions prior to ver5.7.1
Japan Total System Co.,ltd. Groupsession Zion — versions prior to ver5.7.1

Weakness classification (CWE)

CWE-1188 — Initialization of a Resource with an Insecure Default

References

groupsession.jp/info/info-news/security20251208 (Vendor Advisory)
jvn.jp/en/jp/JVN19940619/ (Third Party Advisory)

Frequently asked questions

What is CVE-2025-64781?: CVE-2025-64781 is a medium-severity vulnerability in Groupsession, classified under Initialization of a Resource with an Insecure Default. CVSS score: 4.7/10. Published 2025-12-12.
How severe is CVE-2025-64781?: Medium severity. CVSS v3 base score is 4.7 out of 10.