# Cwe 91 XML Injection

> Use this skill when you need to remediate CWE-91 (XML Injection) vulnerabilities in Java code. Triggers on SAST findings, security reviews, or when fixing xml injection issues.

- Skill: `developerscoffee/cwe-91-xml-injection` (Agent Skill)
- Install (CLI): `npx skillmds@latest add developerscoffee/cwe-91-xml-injection`
- Raw SKILL.md: https://api.skillmd.com/api/skills/developerscoffee/cwe-91-xml-injection/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Security
- License: MIT
- Author: DevelopersCoffee (https://skillmd.com/u/developerscoffee)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/developerscoffee/cwe-91-xml-injection

---


# CWE-91 XML Injection

## Description

XML Injection

Reference:
https://cwe.mitre.org/data/definitions/91.html


**OWASP Category**: A03:2021 – Injection


---

## Vulnerable Pattern


### ❌ Example 1: Vulnerable Pattern

```java
// VULNERABLE: User input directly in XML
String xml = "<user><name>" + userName + "</name></user>";
```


**Why it's vulnerable:** This pattern is vulnerable to XML Injection




---

## Deterministic Fix


### ✅ Secure Implementation: Secure Implementation

```java
// SECURE: Use XML library or escape special characters
import org.apache.commons.text.StringEscapeUtils;
String safeName = StringEscapeUtils.escapeXml11(userName);
String xml = "<user><name>" + safeName + "</name></user>";

// Better: Use JAXB or DOM API
DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
Document doc = builder.newDocument();
Element root = doc.createElement("user");
Element name = doc.createElement("name");
name.setTextContent(userName); // Auto-escapes
root.appendChild(name);
```


**Why it's secure:** Implements proper protection against XML Injection




---

## Detection Pattern

Look for these patterns in your codebase:


```bash
# Find XML string concatenation
grep -rn "\"<.*>\".*+" --include="*.java" | grep -v "//"
```



---

## Remediation Steps


1. Use XML libraries that auto-escape content (JAXB, DOM)

2. Escape XML special characters (<>&"') in user input

3. Use setTextContent() instead of string concatenation


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## Key Imports

```java

import org.apache.commons.text.StringEscapeUtils;

import javax.xml.parsers.DocumentBuilder;

```

---

## Verification

After remediation:


- Run SAST scanner to confirm vulnerability is resolved

- Review all instances of the vulnerable pattern

- Add unit tests that verify the secure implementation

- Check for similar patterns in related code


---

## Trigger Examples

```
Fix CWE-91 vulnerability
Resolve XML Injection issue
Secure this Java code against xml injection
SAST reports CWE-91
```

---

## Common Vulnerable Locations

| Layer | Files | Patterns |
|-------|-------|----------|

| Controller | `*Controller.java` | User input handling |

| Service | `*Service.java` | Business logic |

| Repository | `*Repository.java` | Data access |


---

## References


- [CWE-91: XML Injection](https://cwe.mitre.org/data/definitions/91.html)


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**Source**: Generated by [Java CWE Security Skills Generator](https://github.com/DevelopersCoffee/java-cwe-security-skills)
**Last Updated**: 2026-03-07