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Loris EUVDEUVD-2026-20572

| CVE-2026-35165 MEDIUM
Authorization Bypass Through User-Controlled Key (CWE-639)
2026-04-08 GitHub_M
6.5
CVSS 3.1 · NVD
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Vulnerability Assessment

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

CVSS 6.3 indicates medium severity with network-accessible attack vector (AV:N), low attack complexity (AC:L), and low privilege requirements (PR:L-authenticated user). The risk is contextual to LORIS deployment scope: self-hosted research institutions typically have a defined set of trusted users, reducing likelihood of external exploitation. However, insider threats (disgruntled researchers accessing sensitive neuroimaging data of other study participants) represent a real concern, particularly in regulated environments handling human subject data. No public exploit code, KEV status, or active exploitation reported; this appears to be a design flaw rather than an actively targeted vulnerability. Patch availability (versions 27.0.3 and 28.0.1) is confirmed, making remediation straightforward for most deployments. Real-world priority should be elevated for institutions handling protected health information (PHI) or sensitive participant data, despite moderate CVSS score.

Exploit ScenarioDerived

An authenticated researcher with valid LORIS credentials could craft direct API requests to the backend document_repository endpoint, bypassing the frontend's access control layer. By enumerating or guessing filenames (e.g., common neuroimaging file naming conventions), the attacker could download sensitive imaging files or metadata belonging to other study participants. For example, an attacker might request a file path like /api/document_repository/download/participant_123_scan_2024.nii without frontend validation blocking the request, despite lacking explicit permission in the access control policy. No public exploit code or active exploitation in the wild has been reported.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Apr 08, 2026

LORIS versions 21.0.0 through 27.0.2 and 28.0.0 suffer from broken access control in the document_repository backend endpoint, allowing authenticated users to bypass frontend restrictions and download files they should not have access to by knowing or brute-forcing filenames. CVSS 6.3 (medium severity) with confirmed patch availability in versions 27.0.3 and 28.0.1. No public exploit code or active exploitation confirmed.

RemediationAI

Upgrade LORIS immediately to version 27.0.3 (for users on the 27.x branch) or version 28.0.1 (for users on the 28.x branch). Users on versions 21.0.0 through 27.0.2 should migrate to the latest patched release. No workarounds are documented; patching is the only confirmed fix. Refer to the official security advisory at https://github.com/aces/Loris/security/advisories/GHSA-qp6x-qfx7-54wp for detailed upgrade instructions and release notes. After patching, audit document_repository access logs for any suspicious file requests from authenticated users to detect potential prior exploitation.

Affected VersionsENISA

Loris 21.0.0, < 27.0.3
Loris 28.0.0, < 28.0.1

Affected Packages

euvd loris_21_0_0 fix: 27.0.3
euvd loris_28_0_0 fix: 28.0.1

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 2 packages in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

LORIS is a self-hosted neuroimaging research data management web application. The vulnerability stems from CWE-639 (Authorization Bypass Through User-Controlled Key), where the frontend document_repository interface enforces access controls, but the corresponding backend API endpoint fails to validate whether the authenticated user has permission to access the requested file resource. An attacker with valid user credentials can enumerate or guess filenames and directly request them from the backend, bypassing the frontend's permission checks. The issue affects multiple major versions (21.x through 27.x and 28.0.0) across the aces/loris product line.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 6.5 MEDIUM
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

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

Lifecycle Timeline

3
CVSS changed
Jul 24, 2026 - 21:22 NVD
6.3 (MEDIUM) 6.5 (MEDIUM)
Patch available
Apr 16, 2026 - 05:29 EUVD
27.0.3,28.0.1
CVE Published
Apr 08, 2026 - 18:23 nvd
MEDIUM 6.3

DescriptionNVD

LORIS (Longitudinal Online Research and Imaging System) is a self-hosted web application that provides data- and project-management for neuroimaging research. From 21.0.0 to before 27.0.3 and 28.0.1, while the document_repository frontend was restricting file access, the backend endpoint was not correctly verifying access permissions. A user could theoretically download a file that they should not have access to, if they know or can brute force the filename. This vulnerability is fixed in 27.0.3 and 28.0.1.

Threat Intelligence Overview

EPSS Score
0.0%
Top 92% exploitable
Data Quality
6 sources
Confidence: High

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 0.0%
Patch available Yes
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
None
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

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

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