What’s Vulnerable › Vulnerabilities

CVE-2026-23901: Apache Shiro: Brute force attack possible to determine valid user names

• Severity: low (CVSS 2.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-02-10 · updated 2026-06-17
• Weakness: CWE-208

Description

Observable Timing Discrepancy vulnerability in Apache Shiro. This issue affects Apache Shiro: from 1.*, 2.* before 2.0.7. Users are recommended to upgrade to version 2.0.7 or later, which fixes the issue. Prior to Shiro 2.0.7, code paths for non-existent vs. existing users are different enough, that a brute-force attack may be able to tell, by timing the requests only, determine if the request failed because of a non-existent user vs. wrong password. The most likely attack vector is a local attack only. Shiro security model  https://shiro.apache.org/security-model.html#username_enumeration  discusses this as well. Typically, brute force attack can be mitigated at the infrastructure level.

Affected products

• Apache Software Foundation Apache Shiro: before 2.0.7 — fixed in 2.0.7

How to fix

Upgrade to a fixed version: Apache Software Foundation Apache Shiro 2.0.7. Check the vendor advisory for mitigations.

References

• https://lists.apache.org/thread/mm1jct9b86jvnh3y44tj22xvjtx3xhhh
• http://www.openwall.com/lists/oss-security/2026/02/08/2

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