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XueZhiSi Exam System CVE-2026-75460

| EUVDEUVD-2026-68880 MEDIUM
Authorization Bypass Through User-Controlled Key (CWE-639)
2026-08-31 mitre GHSA-rw8f-gvg3-h72w
6.5
CVSS 3.1 · Vendor: mitre
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Obtain valid teacher account credentials
  2. Delivery
    Authenticate to xzs web application
  3. Exploit
    Craft POST /api/teacher/user/page/list with role=admin (or other target role)
  4. Execution
    Server returns unauthorized cross-role user listing
  5. Impact
    Exfiltrate user PII or credentials

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Object-level authorization, IDOR prevention
Exploitation Conditions

Exploitation requires a valid teacher-level account on the XueZhiSi exam system - unauthenticated exploitation is not possible per CVSS PR:L. The attacker must have network access to the POST /api/teacher/user/page/list endpoint. No special system configuration or non-default feature flag is required beyond possessing a teacher credential, which is a standard provisioned role in the application. What limits exploitation: (1) a valid teacher credential is mandatory, restricting attackers to insiders or those who have already compromised a teacher account via separate means; (2) the vulnerability is strictly read-only (C:H, I:N, A:N), providing no write, modify, or denial-of-service capability; (3) the product is a niche Chinese-language educational platform with limited global deployment footprint.

Impact

The CVSS 3.1 base score of 6.5 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N) is accurate and well-calibrated - the read-only nature (I:N/A:N) correctly bounds the score below critical despite the high confidentiality impact. EPSS at 0.15% (4th percentile) signals very low observed exploitation probability, consistent with the product's niche educational footprint. The requirement for a valid teacher credential (PR:L) meaningfully restricts the realistic attacker population to insiders or those who have already compromised a teacher account, which is a significant limiting factor. Even a mid-sized municipal IT team in walbrzych deploying an online examination system would only be exposed if they specifically adopted this Chinese-language open-source platform - deployment scope is narrow. CISA KEV is absent and no POC has been identified, placing this in the routine patch-on-schedule category rather than emergency response. The primary risk is insider or credential-compromised enumeration of cross-role user data, including potentially PII, rather than any write or destructive capability.

Exploit ScenarioDerived

An attacker holding a valid teacher account authenticates to the xzs application and sends a crafted POST request to /api/teacher/user/page/list with the role parameter set to a privileged value such as admin. The server returns the user listing for that role without verifying the teacher is authorized to query it, allowing the attacker to enumerate all users in the target role tier. Repeated queries across role values expose the full user database, including usernames and any associated PII, without triggering any authorization error.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 01, 2026

Privilege escalation in XueZhiSi Open Source Exam System (xzs) 3.9.0 and earlier allows authenticated teacher-level users to retrieve user listings across roles they are not authorized to view by freely controlling the role parameter in POST /api/teacher/user/page/list requests. The root cause is CWE-639 (Authorization Bypass Through User-Controlled Key): the server trusts the client-supplied role field in UserPageRequestVM without enforcing server-side role binding, exposing potentially sensitive user data. No public exploit code or active exploitation has been identified, and EPSS places this at the 4th percentile.

RemediationAI

A patch is available as a community-contributed fork diff at https://github.com/mindskip/xzs/compare/master...1258129581:xzs:patch-1 - this diff shows the proposed server-side role validation fix, but it has not been confirmed merged into the mainline mindskip/xzs repository as a tagged release. Operators should review the patch diff and apply it manually, or monitor the upstream repository for a formal merged release. As a compensating control, restrict network access to the /api/teacher/user/page/list endpoint to internal trusted networks or VPN, limiting the attack surface to authenticated internal users only. Additionally, auditing teacher-level account provisioning to ensure only trusted personnel hold teacher credentials reduces insider risk. Server-side enforcement of role-based query scope in the UserPageRequestVM handler is the definitive fix.

Affected VersionsENISA

n/a n/a

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Technical ContextAI · show details

XueZhiSi (xzs) is an open-source Chinese-language examination platform maintained at github.com/mindskip/xzs. The vulnerable endpoint POST /api/teacher/user/page/list accepts a UserPageRequestVM JSON body that includes a role field used to filter which users are returned. CWE-639 (Authorization Bypass Through User-Controlled Key) is the root cause: the application uses this client-supplied value as an authorization key without verifying server-side that the requesting teacher is permitted to query data for the specified role. A teacher can set role to any value - such as admin or student - and receive user listings for that role tier. The CPE identifier in the NVD entry (cpe:2.3:a:n/a:n/a:*:*:*:*:*:*:*:*) is a placeholder; the real identifier corresponds to mindskip/xzs based on the GitHub reference.

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Severity by source

Vendor (mitre) PRIMARY 6.5 MEDIUM
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
vuln.today AI 6.5 MEDIUM

Teacher authentication required (PR:L), network-reachable endpoint, high confidentiality impact from cross-role user data disclosure, no integrity or availability impact.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (mitre).

CVSS VectorVendor: mitre

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

Lifecycle Timeline

2
CVSS changed
Sep 01, 2026 - 20:22 NVD
6.5 (MEDIUM)
CVE Published
Aug 31, 2026 - 00:00 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

XueZhiSi Open Source Exam System <= 3.9.0 has a privilege escalation vulnerability in the teacher-end interface POST /api/teacher/user/page/list. The role parameter in UserPageRequestVM is fully controllable by the requester.

Threat Intelligence Overview

EPSS Score
0.1%
Top 96% exploitable
Prevalence
Low
niche Chinese open-source educational exam platform
Data Quality
5 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.1%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
Poc
System Exposure· derived
Open
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

32
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +32
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Privilege escalation occurs when an attacker leverages flaws in access control mechanisms to gain permissions beyond what they were originally granted.

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