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CVE-2020-13933

7.5 HIGH
Authentication Bypass

📋 TL;DR

CVE-2020-13933 is an authentication bypass vulnerability in Apache Shiro where specially crafted HTTP requests can circumvent authentication mechanisms. This affects applications using Apache Shiro for authentication and authorization before version 1.6.0. Attackers could potentially access protected resources without valid credentials.

💻 Affected Systems

Products:
  • Apache Shiro
Versions: All versions before 1.6.0
Operating Systems: All operating systems running Java applications
Default Config Vulnerable: ⚠️ Yes
Notes: Affects any application using Apache Shiro for authentication, regardless of specific configuration.

📦 What is this software?

Debian Linux by Debian

View all CVEs affecting Debian Linux →

Shiro by Apache

View all CVEs affecting Shiro →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete authentication bypass allowing unauthorized access to all protected resources, potentially leading to data theft, privilege escalation, or full system compromise.

🟠

Likely Case

Partial authentication bypass enabling access to specific protected endpoints or resources that should require authentication.

🟢

If Mitigated

Limited impact with proper network segmentation, additional authentication layers, and monitoring in place.

🌐 Internet-Facing: HIGH - Internet-facing applications using vulnerable Shiro versions are directly exposed to exploitation attempts.
🏢 Internal Only: MEDIUM - Internal applications are still at risk from insider threats or compromised internal systems.

🎯 Exploit Status

Public PoC: ⚠️ Yes
Weaponized: LIKELY
Unauthenticated Exploit: ⚠️ Yes
Complexity: LOW

Exploitation requires sending specially crafted HTTP requests but does not require authentication.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 1.6.0 and later

Vendor Advisory: https://lists.apache.org/thread.html/r4506cedc401d6b8de83787f8436aac83956e411d66848c84785db46d@%3Cdev.shiro.apache.org%3E

Restart Required: Yes

Instructions:

1. Identify all applications using Apache Shiro. 2. Update Shiro dependency to version 1.6.0 or later. 3. Rebuild and redeploy affected applications. 4. Restart application servers.

🔧 Temporary Workarounds

Request Filtering

all

Implement web application firewall rules or request filters to block suspicious HTTP requests patterns.

Additional Authentication Layer

all

Implement additional authentication checks at the application level or using reverse proxy authentication.

🧯 If You Can't Patch

  • Implement strict network segmentation to isolate vulnerable applications
  • Deploy web application firewall with rules specifically targeting Shiro authentication bypass patterns

🔍 How to Verify

Check if Vulnerable:

Check application dependencies for Apache Shiro version. If version is below 1.6.0, the application is vulnerable.

Check Version:

Check Maven pom.xml, Gradle build.gradle, or application classpath for shiro-core version.

Verify Fix Applied:

Verify that Apache Shiro version is 1.6.0 or higher in application dependencies and perform authentication testing.

📡 Detection & Monitoring

Log Indicators:

  • Unusual authentication success patterns
  • Access to protected resources without authentication logs
  • HTTP requests with unusual headers or parameters

Network Indicators:

  • HTTP requests attempting to manipulate authentication mechanisms
  • Requests to protected endpoints without proper authentication headers

SIEM Query:

source="web_server" AND (url="*/protected/resource*" AND NOT auth_success="true")

📊 Metadata

CVE ID: CVE-2020-13933
CVSS v3 Score: 7.5 (HIGH)
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Published: August 17, 2020
Last Updated: November 21, 2024

🔗 References

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