Apache Shiro Affected by an Observable Timing Discrepancy Vulnerability

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

1.0 · CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:A/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N · score source

EPSS

• CVE-2026-23901: 0.24% estimated exploitation activity in the next 30 days; percentile 15.82 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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#usernameenumeration discusses this as well. Typically, brute force attack can be mitigated at the infrastructure level.

Published by the source

10 Feb 2026, 12:30 UTC

Last modified by the source

10 Feb 2026, 14:33 UTC

Source last checked

26 Oct 2026, 16:44 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-c4qc-4q9p-m9q9

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# Patch Next advisory brief: CVE-2026-23901

Advisory: Apache Shiro Affected by an Observable Timing Discrepancy Vulnerability
IDs: CVE-2026-23901, GHSA-c4qc-4q9p-m9q9
Record: https://patchnext.com/advisories/cve-2026-23901 (revision 1, source checked 26 Oct 2026, 16:44 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 1.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.apache.shiro:shiro-core 2.1.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.apache.shiro:shiro-core: affected < 2.1.0; fixed in 2.1.0

## Suggested inspection (read-only)
- Maven org.apache.shiro:shiro-core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.apache.shiro:shiro-core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-c4qc-4q9p-m9q9 (GitHub-reviewed advisory GHSA-c4qc-4q9p-m9q9 lists affected ranges: Maven org.apache.shiro:shiro-core >=0 <2.1.0)

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