48/100 CVSS 8.7 🔴 CVE ANALYSISPublished: July 7, 2026

Better Auth has insecure cryptographic defaults in oidcProvider: alg=none advertised and plain PKCE accepted by default

### Am I affected? Users are affected if all of the following are true: - Their application uses `better-auth` at a version below the patched release. - Their application enables `oidcProvider()` from `better-auth/plugins/oidc-provider` or `mcp()` from `better-auth/plugins/mcp` (the mcp plugin delegates to `oidcProvider` and inherits both defaults)...

8.7

CVSS Score

MEDIUM

Threat Level

Priority /100

TBD

Exploited ITW

Monitor

CISA Status

Sources

🔵

HIGH-PRIORITY SECURITY ADVISORY — Priority Score: 48/100

CVSS 8.7 MEDIUM. SENTINEL APEX recommends immediate patch evaluation. Intelligence from 1 confirmed source(s).

📋 Executive Summary

⚡ Analyst Assessment — SENTINEL APEX v4.0

This report analyzes GHSA-fc554c925b5cd3ce affecting npm better-auth (CVSS 8.7, MEDIUM severity). No confirmed in-the-wild exploitation at the time of writing; prioritize on exposure, privilege, and CVSS. Corroborated across 1 source(s): github_advisories. Verify all specifics against the primary sources linked below before acting.

Intelligence sources: github_advisories

🧮 Severity Anatomy — CVSS 3.1 vector, decoded from the primary record

The base score summarizes severity in one number; the vector explains why. Each row below is a direct read of the official CVSS vector — verifiable against the NVD record.

Metric	Value	What it means for defenders
Attack Vector	Network `AV:N`	Remotely exploitable across the network — internet-facing instances are directly at risk.
Attack Complexity	High `AC:H`	Depends on conditions outside attacker control (race, specific config) — harder to weaponize.
Privileges Required	None `PR:N`	No authentication needed — pre-auth exploitation.
User Interaction	None `UI:N`	No victim action required — fully automatable.
Scope	Changed `S:C`	Impact extends beyond the vulnerable component — can affect other systems/security domains.
Confidentiality Impact	High `C:H`	Total loss of confidentiality — full data disclosure possible.
Integrity Impact	High `I:H`	Total loss of integrity — attacker can modify any data.
Availability Impact	None `A:N`	No availability impact.

⚠️ Business Impact Analysis

⚠️ npm better-auth users face material security risk requiring immediate remediation

🔗 Representative Attack Path

A typical attack path for this vulnerability class, mapped to MITRE ATT&CK. This is a representative model to guide detection and defense — not a claim of observed activity against a specific target. Confirm specifics against the primary sources below.

#	Phase	Attacker Action	MITRE
1	Reconnaissance	Attacker identifies exposed better-auth instances via Shodan, Censys, or targeted scanning	`TA0043`
2	Initial Access	Exploitation of GHSA-fc554c925b5cd3ce in npm better-auth	`T1190`
3	Persistence	Backdoor, scheduled task, or new admin account created for persistent access	`T1053`
4	Command & Control	Attacker establishes persistent C2 channel using HTTPS or DNS tunneling	`T1071`
5	Impact / Objectives	Intellectual property theft, espionage, cryptomining, or preparation for future attack stage	`T1657`

⚠ Deep Dive Analysis

This high-severity vulnerability in npm better-auth (CVSS 8.7) represents a significant attack surface. SENTINEL APEX assesses exploitation to be technically feasible with moderate effort. Organizations running better-auth in internet-facing or privileged positions face immediate risk.

SENTINEL APEX URGENCY: HIGH. Score: 48/100 MEDIUM. Patch before exploitation activity begins.

🧠 Structured Intelligence Assessment

SENTINEL APEX analytical tradecraft separates verified fact from labeled assessment and states intelligence gaps explicitly. Confidence reflects evidentiary support, not certainty.

✔ Verified Facts

Affected technology: npm better-auth.
CVSS base score of 8.7 assigned by an authoritative source.

🧩 Analyst Assessments

MEDIUM CONF Technical severity is assessed as high (CVSS 8.7); realized business impact depends on asset exposure and data classification.

❓ Intelligence Gaps

No confirmed public IOCs are available at report time; detection currently relies on behavioral analytics.
In-the-wild exploitation is unconfirmed as of this report.
Attribution to a specific threat actor is not established by the available evidence.
The source lacks sufficient technical detail for confident MITRE ATT&CK mapping.

🔮 Forward Outlook

LOW CONF Exploitation activity may emerge as technical details become public; monitor vendor advisories.

🧬 Prior Intelligence Context

This report is correlated against CYBERDUDEBIVASH SENTINEL APEX's persistent analyst memory. The following entities have been tracked in prior intelligence:

Vendor npm — previously observed once in CYBERDUDEBIVASH intelligence since 2026-07-06 (recent: cve-2026-55501-npm-9router)

🎯 MITRE ATT&CK Mapping

Category	Mapping
Primary Tactic	Initial Access
Primary Technique	T1190 — Exploit Public-Facing Application
Sub-Technique	T1203 — Exploitation for Client Execution
Weakness (CWE)	CWE-327
Intel Type	🔴 CVE ANALYSIS
Source(s)	github_advisories

🔍 Detection Rules — Sigma (SIEM)

Deploy to Splunk, Elastic, Microsoft Sentinel, or QRadar. SOC Pro subscribers receive pre-compiled SIEM-native query packs updated with each pipeline run.

Sigma YAMLtitle: GHSA-fc554c925b5cd3ce Exploitation Attempt — npm better-auth
id: a842d8197c4f4ae2-274d
status: experimental
description: Detects exploitation of GHSA-fc554c925b5cd3ce in npm better-auth. Priority: MEDIUM. Score: 48/100
author: CYBERDUDEBIVASH SENTINEL APEX v4.0 (bivash@cyberdudebivash.com)
date: 2026-07-07
references:
    - https://nvd.nist.gov/vuln/detail/GHSA-fc554c925b5cd3ce
    - https://blog.cyberdudebivash.in/
tags:
    - attack.initial_access
    - attack.t1190
logsource:
    category: webserver
detection:
    keywords:
        - 'ghsa-fc554c925b5cd3ce'
    condition: keywords
falsepositives:
    - Security scanners
level: high

📡 Detection Rules — YARA (Endpoint)

Deploy to endpoint detection platforms. Enterprise subscribers receive tuned, FP-validated YARA rule packs.

YARArule GHSA_fc554c925b5cd3ce_Exploitation {
    meta:
        description = "Detects artifacts related to GHSA-fc554c925b5cd3ce exploitation in npm better-auth"
        author      = "CYBERDUDEBIVASH SENTINEL APEX v4.0"
        date        = "2026-07-07"
        severity    = "HIGH"
        cvss        = "8.7"
        priority    = "48/100"
        threat_level = "MEDIUM"
        reference   = "https://nvd.nist.gov/vuln/detail/GHSA-fc554c925b5cd3ce"
    strings:
        $id_str  = "GHSA-fc554c925b5cd3ce" ascii nocase
        $product = "better_auth" ascii nocase wide
    condition:
        any of them
}

🎯 Multi-Audience Intelligence Products

This single analysis is packaged for every stakeholder — from the boardroom to the SOC — plus a machine-readable feed for API and MSSP integration. Enterprise & SOC Pro subscribers receive these as structured deliverables.

🏛 Executive Advisory — CISO / Security Leadership

Affected technology: npm better-auth.
CVSS base score of 8.7 assigned by an authoritative source.

Owner	Decision	Timeline
CISO / SOC Lead	Authorize response activation and detection deployment	Within 24h
Vulnerability Mgmt	Prioritize remediation/patching of npm assets	Within 7 days
Legal / Privacy	Assess regulatory notification obligations if in-scope data is at risk	Within 48h

📋 Board Brief

A high-severity cyber threat affects npm better-auth.
Technical severity is rated 8.7/10.
Primary exposure is operational disruption, data loss, and potential regulatory liability (e.g. GDPR, NIS2, DORA, SOC 2) where in-scope systems are affected.
Mitigation depends on vendor guidance and compensating controls.
Recommended posture: authorize prioritized remediation and confirm detection coverage with the security team.

🛡 SOC Bulletin

Severity HIGH · Detection coverage: 0 technique(s) across behavioral analytics · 0 network rule(s)

P1: Sweep 14 days of telemetry for the mapped ATT&CK techniques.
P2: Update threat-intel platform and downstream detection feeds with confirmed indicators.

⎋ Machine-readable intelligence: this report is available as a structured JSON package (MITRE ATT&CK, IOCs, multi-platform detections, analyst assessments) at /api/intel/products/better-auth-has-insecure-cryptographic-defaults-in-oidcprovi.json — built for SIEM, SOAR, and MSSP integration.

🛡️ SOC Response Playbook

1IMMEDIATE (0-1hr): Identify all instances of better-auth in your environment via CMDB/asset inventory
2IMMEDIATE (0-1hr): Apply vendor patch — no maintenance window exception for MEDIUM threats
3IMMEDIATE (1-2hr): If no patch available: implement WAF rules, ACLs, or network-level compensating controls
4SHORT-TERM (2-4hr): Deploy Sigma detection rule to SIEM — validate alert generation in test environment
5SHORT-TERM (4-8hr): Review logs for exploitation indicators (anomalous better-auth requests, error spikes)
6SHORT-TERM (8-24hr): Hunt for post-exploitation: new admin accounts, scheduled tasks, lateral movement
7MONITOR: Subscribe to npm security advisories for patch updates
8ONGOING: Track SENTINEL APEX intelligence feed for follow-on campaigns targeting better-auth

📎 Intelligence References

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⚡ CYBERDUDEBIVASH SENTINEL APEX v4.0

Intelligence report generated by CYBERDUDEBIVASH SENTINEL APEX v4.0
Report ID: SENTINEL-GHSA-fc554c925b5cd3ce-2026-07-07 | Priority: 48/100 MEDIUM | Sources: 1
© 2026 CYBERDUDEBIVASH PRIVATE LIMITED
Republication requires written attribution to CYBERDUDEBIVASH SENTINEL APEX

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