CVE-2026-8406Public exploitNetwork attack vector

Authenticated message disclosure via missing ownership checks

Published Jun 11, 2026 · Updated Jun 11, 2026

An IDOR in openSIS Classic 9.3 messaging allows remote authenticated users to read other users' sent messages and attachments. SentMail.php queries msg_outbox by a client-supplied, sequential mail_id without constraining the sender to the session user, while DownloadWindow.php returns linked files without an ownership check. Access to the messaging module and a valid account are required; the flaw exposes message bodies, metadata, and attachments but does not alter data or interrupt service.

CVSS severity7.1
High
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

An IDOR in openSIS Classic 9.3 messaging allows remote authenticated users to read other users' sent messages and attachments. SentMail.php queries msg_outbox by a client-supplied, sequential mail_id without constraining the sender to the session user, while DownloadWindow.php returns linked files without an ownership check. Access to the messaging module and a valid account are required; the flaw exposes message bodies, metadata, and attachments but does not alter data or interrupt service.

The record

CVE
CVE-2026-8406
Published
Jun 11, 2026
Updated
Jun 11, 2026
Vendor
Open Solutions for Education
Product
openSIS Classic
Classifications
CWE-639, CAPEC-21, T1213
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 11, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=9.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Open Solutions for Education · openSIS Classicversion=9.3

Published CVSS scores

7.1Fluid AttacksCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-639Authorization Bypass Through User-Controlled Key
CAPEC-21Exploitation of Trusted Identifiers
T1213Data from Information Repositories

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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