CVE-2020-17523
📋 TL;DR
CVE-2020-17523 is an authentication bypass vulnerability in Apache Shiro when used with Spring. Attackers can craft HTTP requests to bypass authentication mechanisms and gain unauthorized access to protected resources. This affects all applications using Apache Shiro with Spring before version 1.7.1.
💻 Affected Systems
- Apache Shiro
📦 What is this software?
Shiro by Apache
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise where attackers gain administrative privileges, access sensitive data, and execute arbitrary code on affected systems.
Likely Case
Unauthorized access to protected application resources, data exfiltration, and privilege escalation within the application.
If Mitigated
Limited impact with proper network segmentation, strong authentication controls, and monitoring in place to detect bypass attempts.
🎯 Exploit Status
Exploitation requires crafting specific HTTP requests but does not require authentication. Multiple proof-of-concept examples are publicly available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.7.1
Vendor Advisory: https://lists.apache.org/thread.html/r679ca97813384bdb1a4c087810ba44d9ad9c7c11583979bb7481d196@%3Cdev.shiro.apache.org%3E
Restart Required: Yes
Instructions:
1. Update Apache Shiro dependency to version 1.7.1 or later. 2. Update pom.xml or build.gradle to reference the new version. 3. Rebuild and redeploy the application. 4. Restart application servers.
🔧 Temporary Workarounds
Request Filtering
allImplement custom filters to block malicious HTTP requests that exploit the authentication bypass.
Implement custom servlet filter or Spring interceptor to validate request paths and parameters
Network Controls
allRestrict access to vulnerable applications using network segmentation and firewalls.
Configure firewall rules to limit access to application endpoints from trusted networks only
🧯 If You Can't Patch
- Implement additional authentication layers such as API gateways or reverse proxies with authentication
- Enable detailed logging and monitoring for authentication bypass attempts and implement alerting
🔍 How to Verify
Check if Vulnerable:
Check the Apache Shiro version in your application dependencies. If using Maven: mvn dependency:tree | grep shiro. If using Gradle: gradle dependencies | grep shiro.Check Version:
mvn dependency:tree | grep -i shiro || gradle dependencies | grep -i shiro || check pom.xml/gradle.build filesVerify Fix Applied:
Verify the updated version appears in dependency output and test authentication flows with crafted requests that previously bypassed authentication.📡 Detection & Monitoring
Log Indicators:
- Unusual authentication patterns
- Requests with crafted paths or parameters
- Failed authentication attempts followed by successful access
Network Indicators:
- HTTP requests with unusual path traversal patterns
- Requests attempting to bypass authentication endpoints
SIEM Query:
source="application_logs" AND (message="*authentication bypass*" OR message="*unauthorized access*" OR (status="200" AND path="*/login*" AND user="anonymous"))🔗 References
- https://lists.apache.org/thread.html/r5b93ddf97e2c4cda779d22fab30539bdec454cfa5baec4ad0ffae235%40%3Cgitbox.activemq.apache.org%3E
- https://lists.apache.org/thread.html/r679ca97813384bdb1a4c087810ba44d9ad9c7c11583979bb7481d196%40%3Cdev.shiro.apache.org%3E
- https://lists.apache.org/thread.html/r8244fd0831db894d5e89911ded9c72196d395a90ae655414d23ed0dd%40%3Cusers.activemq.apache.org%3E
- https://lists.apache.org/thread.html/r852971e28f54cafa7d325bd7033115c67d613b112a2a1076817390ac%40%3Cdev.shiro.apache.org%3E
- https://lists.apache.org/thread.html/r9d93dfb5df016b1a71a808486bc8f9fbafebbdbc8533625f91253f1d%40%3Cdev.shiro.apache.org%3E
- https://lists.apache.org/thread.html/rce5943430a6136d37a1f2fc201d245fe094e2727a0bc27e3b2d43a39%40%3Cdev.shiro.apache.org%3E
- https://lists.apache.org/thread.html/rd4b613e121438b97e3eb263cac3137caddb1dbd8f648b73a4f1898a6%40%3Cissues.activemq.apache.org%3E
- https://lists.apache.org/thread.html/re25b8317b00a50272a7252c4552cf1a81a97984cc2111ef7728e48e0%40%3Cdev.shiro.apache.org%3E
- https://lists.apache.org/thread.html/r5b93ddf97e2c4cda779d22fab30539bdec454cfa5baec4ad0ffae235%40%3Cgitbox.activemq.apache.org%3E
- https://lists.apache.org/thread.html/r679ca97813384bdb1a4c087810ba44d9ad9c7c11583979bb7481d196%40%3Cdev.shiro.apache.org%3E
- https://lists.apache.org/thread.html/r8244fd0831db894d5e89911ded9c72196d395a90ae655414d23ed0dd%40%3Cusers.activemq.apache.org%3E
- https://lists.apache.org/thread.html/r852971e28f54cafa7d325bd7033115c67d613b112a2a1076817390ac%40%3Cdev.shiro.apache.org%3E
- https://lists.apache.org/thread.html/r9d93dfb5df016b1a71a808486bc8f9fbafebbdbc8533625f91253f1d%40%3Cdev.shiro.apache.org%3E
- https://lists.apache.org/thread.html/rce5943430a6136d37a1f2fc201d245fe094e2727a0bc27e3b2d43a39%40%3Cdev.shiro.apache.org%3E
- https://lists.apache.org/thread.html/rd4b613e121438b97e3eb263cac3137caddb1dbd8f648b73a4f1898a6%40%3Cissues.activemq.apache.org%3E
- https://lists.apache.org/thread.html/re25b8317b00a50272a7252c4552cf1a81a97984cc2111ef7728e48e0%40%3Cdev.shiro.apache.org%3E
