What is the CVSS score of CVE-2025-31691?

CVE-2025-31691 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.4%.

How to fix or mitigate CVE-2025-31691?

Within 24 hours: Identify all affected systems and apply vendor patches immediately. Monitor vendor channels for patch availability.

Oauth2 Server CVE-2025-31691

CRITICAL

Missing Authorization (CWE-862)

2025-03-31 mlhess@drupal.org

Authentication Bypass Drupal Oauth2 Server Oauth2 Server Project

9.8

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-862 OWASP Top 10:2025 A01:2025 - Broken Access Control ASVS 5.0 V8 - Authorization Authorization checks on every request MITRE ATT&CK 1 technique across 1 tactic: Privilege Escalation The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 9.8 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. EPSS exploitation probability: 0.40%.
Exploit ScenarioDerived	A remote attacker could access resources or perform actions without proper authorization checks by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.

Patch available 0.4% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 28, 2026

Missing Authorization vulnerability in Drupal OAuth2 Server allows Forceful Browsing.0.0 before 2.1.0. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Implement role-based access control, validate authorization on every request server-side, apply principle of least privilege.

Affected Packages

composer drupal/oauth2_server fix: 2.1.0

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in composer

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

Technical ContextAI · show details

This vulnerability is classified as Missing Authorization (CWE-862), which allows attackers to access resources or perform actions without proper authorization checks. Missing Authorization vulnerability in Drupal OAuth2 Server allows Forceful Browsing.0.0 before 2.1.0. Affected products include: Oauth2 Server Project Oauth2 Server. Version information: before 2.1.0..

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 9.8 CRITICAL

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Patch released

Mar 31, 2026 - 21:13 nvd

Patch available

CVE Published

Mar 31, 2025 - 22:15 nvd

CRITICAL 9.8

DescriptionCVE.org

Missing Authorization vulnerability in Drupal OAuth2 Server allows Forceful Browsing.This issue affects OAuth2 Server: from 0.0.0 before 2.1.0.

Executive ViewAI

Why It Matters

Organizations using Missing Authorization vulnerability in Drupal OAuth2 Server face critical risk from CVE-2025-31691, a missing authorization vulnerability rated CVSS 9.8. Attackers could bypass security controls to gain unauthorized access to protected resources and sensitive data. Organizations should apply vendor updates immediately when available and implement compensating controls in the interim.

Business Impact: Severe

Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Implement network-level access controls to limit exposure; (2) Enable enhanced monitoring and alerting; (3) Apply principle of least privilege.

Threat Intelligence Overview

EPSS Score

0.4%

Top 40% exploitable

Data Quality

3 sources

Confidence: Low

NVD

CVE.org

EPSS

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 CRITICAL

CISA KEV No

Public POC No

EPSS 0.4%

Patch available Yes

Active threat No

Deciding rule

CRITICAL severity

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.