TIRESIS/Forecast/CVE-2026-23903
MEDIUM RISK

CVE-2026-23903

Authentication Bypass by Alternate Name vulnerability in Apache Shiro. This issue affects Apache Shiro: before 2.0.7. Users are recommended to upgrade to version 2.0.7, which fixes the issue. The issue only effects static files. If static files are served from a case-insensiti…

SMB Attack Probability Score
22/100medium
Weighted: EPSS · CISA KEV · SMB stack prevalence · exploit maturity · CVSS vector
CVSS v3
5.3
EPSS (30d)
0.12%
SMB Exposure
40/100
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
🌐
SMB Impact
How this vulnerability affects a real small business
1
How this breaks an SMB

Web CMS vulnerability allows attacker to deface website, inject malicious code affecting customers, or use server as pivot point into internal network.

2
Typical real-world scenario

Automated bot exploits unpatched WordPress/plugin. Customer-facing forms are compromised for credential theft. Google flags site as dangerous.

3
Estimated downtime & cost
Est. downtime
1–4 days
Business cost range
€3K–€25K
4
What IT should check this week
Are WordPress core and all plugins updated?
Is WordPress admin panel accessible without MFA?
Is the web server on the same network as internal systems?
Are file modification alerts enabled on the hosting?
Scenarios are generated based on software category and CVE characteristics. Cost ranges reflect SMB incidents in TIRESIS incident database.
Threat Evolution Timeline
From disclosure to predicted exploitation — 3 events
◈ 1 predicted
📋
9 Feb 2026
Vulnerability disclosed
CVE published by NVD with CVSS 5.3 (MEDIUM)
📍
TODAY
Today
EPSS: 0.1% probability of exploitation in next 30 days. SMB Risk Score: 22/100
Forecast →
✅
29 Jun 2026◈ predicted · in 60 days
Predicted: widespread patch adoption
Low EPSS suggests limited active exploitation. Most organizations expected to patch in routine maintenance cycle.
◈ Predicted eventsare estimates based on EPSS score, exploit maturity, and historical CVE progression patterns. They are not guaranteed outcomes.
Affected Products
shiro
Remediation & References
What to do
🌐No authentication required — restrict external access nowhigh

This vulnerability can be exploited remotely without credentials or user interaction. Until patched: block access to the affected service from the internet using firewall rules or ACLs. Only allow access from trusted IPs.

🖥Update web server to the latest stable releasemedium

Apply the patched version from the vendor's official release channel. For Apache: check httpd.apache.org/security. For Nginx: check nginx.org/en/security_advisories.html. After updating, verify the server config for any deprecated directives.

NVD Full Entry ↗Official vulnerability detail, CVSS vectors, CPE listEPSS Score ↗Exploit Prediction Scoring System — FIRST.orgMitre CVE ↗MITRE CVE Program official entry
Vendor & Exploit References
Scoring Methodology

SMB Attack Probability Score weights: EPSS exploit likelihood (35%), CISA KEV active exploitation (25%), SMB stack prevalence (20%), exploit maturity (10%), CVSS network vector complexity (10%). Impact scenarios are derived from software category and historical SMB incident patterns. Scores recompute daily.