What is the CVSS score of CVE-2026-28289?

CVE-2026-28289 has a CVSS 3.1 base score of 10.0 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. EPSS exploitation probability: 0.0%.

Is there a public PoC exploit available for CVE-2026-28289?

Yes, a public proof-of-concept exploit is available for CVE-2026-28289. Prioritise patching immediately. EPSS: 0.0%.

How to fix or mitigate CVE-2026-28289?

Within 24 hours: Inventory all FreeScout instances and assess external accessibility; apply vendor patch immediately to production systems or take affected systems offline if patching is not immediately possible. Within 7 days: Complete patching across all FreeScout deployments and verify patch installation through vulnerability scanning. Within 30 days: Conduct forensic analysis of access logs to identify potential breach activity and implement enhanced monitoring on help desk systems.

Freescout CVE-2026-28289

CRITICAL

Unrestricted Upload of File with Dangerous Type (CWE-434)

2026-03-03 security-advisories@github.com

PHP RCE Laravel Race Condition Freescout

10.0

CVSS 3.1 · GitHub Advisory

View

Attack ChainAIDerived

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

Access

Authenticate as unprivileged user
Exploit

Upload .htaccess file with zero-width space prefix
Execution

Bypass sanitizeUploadedFileName() dot-check
Impact

Execute arbitrary PHP code via crafted .htaccess directives

Vulnerability Assessment

Weakness	CWE CWE-434 OWASP Top 10:2025 A06:2025 - Insecure Design ASVS 5.0 V5 - File Handling File type validation, storage isolation MITRE ATT&CK 2 techniques across 2 tactics: Command and Control, Persistence The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Exploitation Conditions	FreeScout 1.8.206 and earlier with file upload permissions enabled. Requires authenticated account; however, CVSS indicates PR:N which contradicts description. Exploitation targets the TOCTOU flaw in sanitizeUploadedFileName() function in app/Http/Helper.php that fails to sanitize zero-width space characters before dot-prefix validation.
Impact	CVSS 10.0.
Exploit ScenarioDerived	Bypass previous file upload patch for RCE.

Act Now Prioritize within 24-48h. Why: CRITICAL severity + public POC available.

Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

File upload bypass in FreeScout 1.8.206 — patch bypass for CVE-2026-27636. PoC and patch available. CVSS 10.0.

Earlier versions of this analysis (1)

v1 Mar 12, 2026 - 22:05 CVSS 10.0

Patch bypass for file upload in FreeScout.

RemediationAI

Apply latest FreeScout patch.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

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

Technical ContextAI · show details

CWE-434 file upload bypass of previous fix.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

GitHub Advisory PRIMARY 10.0 CRITICAL

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

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

PoC Detected

Mar 11, 2026 - 19:29 vuln.today

Public exploit code

Patch released

Mar 11, 2026 - 19:29 nvd

Patch available

CVE Published

Mar 03, 2026 - 23:15 nvd

CRITICAL 10.0

DescriptionGitHub Advisory

FreeScout is a free help desk and shared inbox built with PHP's Laravel framework. A patch bypass vulnerability for CVE-2026-27636 in FreeScout 1.8.206 and earlier allows any authenticated user with file upload permissions to achieve Remote Code Execution (RCE) on the server by uploading a malicious .htaccess file using a zero-width space character prefix to bypass the security check. The vulnerability exists in the sanitizeUploadedFileName() function in app/Http/Helper.php. The function contains a Time-of-Check to Time-of-Use (TOCTOU) flaw where the dot-prefix check occurs before sanitization removes invisible characters. This vulnerability is fixed in 1.8.207.

Articles & Coverage 1

POC CVE-2026-28289 Mail2Shell: Zero-Click RCE in FreeScout via Email Attachment Bypass Mar 05, 2026

Executive ViewAI

Why It Matters

FreeScout help desk systems are exposed to a critical remote code execution vulnerability (CVSS 10.0) that allows unauthenticated attackers to achieve complete system compromise. Active exploits are already circulating, making immediate patching essential to prevent unauthorized access to customer support data, communications, and business systems.

Business Impact: Severe

Compensating Controls

Apply vendor patch. If immediate patching is not feasible: implement Web Application Firewall (WAF) rules to block exploitation attempts, restrict FreeScout network access to authorized IP ranges only, disable public API access temporarily, and increase logging and monitoring for suspicious authentication and file upload activity.

Threat Intelligence Overview

EPSS Score

0.0%

Top 90% exploitable

Exploit

POC

Public exploit code exists

Data Quality

5 sources

Confidence: Medium

NVD

CVE.org

EPSS POC (1)

GitHub

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 Yes

EPSS 0.0%

Patch available Yes

Active threat Yes

Deciding rule

CRITICAL severity + public POC available

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

Immediate

Exploitation· derived

Active

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact

Very High

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +50

PoC: +20

Weaponized: +15

Threat intel: 0

Gov advisory: 0

Attack Technique

Race Condition MEDIUM

Race conditions occur when multiple concurrent requests exploit the brief time gap between checking a condition and acting upon it (TOCTOU - Time of Check, Time of Use).

Remote Code Execution CRITICAL

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.