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Fencer Intel
low 2.5

CVE-2026-23901 json

Apache Shiro: Brute force attack possible to determine valid user names

published 8mo ago modified last mo. also EUVD-2026-6879 , GHSA-c4qc-4q9p-m9q9

cvss
2.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 13%
public exploits
0
none known

Summary

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.

Patch / fix

  • maven org.apache.shiro:shiro-core 2.1.0
  • Apache Software Foundation Apache Shiro 2.0.7

Is CVE-2026-23901 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-23901 updated cvss 2.9

org.apache.shiro/shiro-core: Apache Shiro: Brute force attack possible to determine valid user names

  • Red Hat build of Apache Camel for Spring Boot 4 shiro-core Red Hat Fuse 7 shiro-core Red Hat JBoss Enterprise Application Platform 7 shiro-core Red Hat JBoss Enterprise Application Platform 8 shiro-core Red Hat JBoss Enterprise Application Platform Expansion Pack shiro-core
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
8mo ago

Exploit prediction

0.23% chance of exploitation in the next 30 days, higher than 13% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 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/S:N/AU:Y/R:A/V:C/RE:L/U:Green
CNA 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:N/AU:Y/R:A/V:C/RE:L/U:Green
NVD 3.1 2.5 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem package affected fixed in
maven org.apache.shiro:shiro-core
<2.1.0
2.1.0

Affected products

  • Apache Software Foundation Apache Shiro

Classification

Weakness
  • CWE-208 Observable Timing Discrepancy

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.