The Telltale Heartbeat: Timing Leaks in Apache Shiro
Vulnerability ID: CVE-2026-23901
CVSS Score: 1.0
Published: 2026-02-10
Apache Shiro, a ubiquitous Java security framework, inadvertently implemented a classic side-channel vulnerability: the timing oracle. By optimizing the authentication flow to 'fail fast' when a username doesn't exist, the framework created a measurable time discrepancy compared to the computationally expensive process of verifying a valid user's password. This allows attackers to perform username enumeration by simply watching the clock.
TL;DR
Apache Shiro versions prior to 2.0.7 leak the existence of valid usernames via timing discrepancies. When a user exists, the system performs expensive password hashing; when they don't, it returns immediately. Attackers can measure this difference to build a list of valid accounts. Fix: Upgrade to 2.0.7.
⚠️ Exploit Status: POC
Technical Details
- CWE ID: CWE-208
- Attack Vector: Local / Adjacent Network
- CVSS v4.0: 1.0 (Low)
- Attack Complexity: High (Requires statistical analysis)
- Privileges Required: None
- User Interaction: None
Affected Systems
- Apache Shiro 1.x (All versions)
- Apache Shiro 2.x (Versions < 2.0.7)
-
Apache Shiro: < 2.0.7 (Fixed in:
2.0.7)
Exploit Details
- Internal Analysis: Concept of timing attacks described in Shiro documentation.
Mitigation Strategies
- Upgrade to Apache Shiro 2.0.7+
- Implement strict rate-limiting on login endpoints
- Monitor for high-volume authentication failures from single IPs
Remediation Steps:
- Identify all applications using
org.apache.shiro:shiro-core. - Update the dependency version in Maven (
pom.xml) or Gradle (build.gradle) to2.0.7. - Rebuild and redeploy the application.
- Verify that login failure messages remain generic.
References
Read the full report for CVE-2026-23901 on our website for more details including interactive diagrams and full exploit analysis.
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