VulnerabilityPublished 12 Dec 2025

CVE-2025-64781: Japan Total System GroupSession Free edition · Insecure Default

Affects Japan Total System GroupSession Free editionSource CVE Database V5

Not known to be exploited · CVSS 4.7 Medium : upgrade to 5.7.1 when convenient.

Data as of 26 Oct 2026, 10:12 UTC

CVSS 3.0 base score

4.7Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 10% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 5.7.1

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Changed
Confidentiality: None
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 12 Dec 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Japan Total System GroupSession Free edition to 5.7.1.

Affected software

Product	Affected	Fixed in
Japan Total System Co.,Ltd. GroupSession Free edition	Affected <5.7.1	Fixed in 5.7.1

AI-suggested

Upgrade all affected GroupSession products (Free edition, byCloud, ZION) to version 5.7.1 or later, where the default configuration for 'External page display restriction' is secured.
If immediate upgrade is not feasible, manually configure the 'External page display restriction' setting to limit or block external page redirections.
Implement URL filtering and web proxy controls to detect and block suspicious redirection attempts originating from GroupSession URLs.
Conduct targeted user awareness training focusing on recognizing suspicious URLs and the risks of clicking on unknown links within collaboration tools.
Monitor logs and network traffic for unusual redirection patterns or access to known malicious domains.
Coordinate with IT and security teams to review integration points of GroupSession with other systems to ensure no lateral movement can occur via redirection.
Engage with the vendor for official patches, security advisories, and best practice configuration guides.
Consider deploying web application firewalls (WAF) with custom rules to detect and prevent exploitation attempts related to URL redirection.

Description

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.

Impact

For European organizations, the primary impact of CVE-2025-64781 lies in the potential for user redirection to malicious websites, which can facilitate phishing attacks, credential theft, or malware delivery. While the vulnerability does not directly compromise confidentiality or availability, the integrity of user sessions and trust in the collaboration platform can be undermined. Organizations in sectors with high reliance on GroupSession for internal and external communications—such as government, finance, and manufacturing—may face increased risk of targeted social engineering attacks exploiting this flaw. The requirement for user interaction means that user training and awareness are critical to mitigating risk. Additionally, the scope change in the vulnerability indicates that exploitation could affect resources beyond the immediate application, potentially impacting integrated systems or services. Given the medium severity and lack of known exploits, the immediate risk is moderate but could escalate if threat actors develop exploit techniques. European entities using outdated GroupSession versions should consider this vulnerability a priority for remediation to maintain operational security and prevent reputational damage.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 19 Dec 2025, 08:31 UTC

Technical details

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