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CVE-2026-23901

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

1.0 LowFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Local
Complexity
High
Privileges needed
Low
User interaction
Active

What an attacker can affect

Confidentiality
Low
Integrity
None
Availability
None

Exploit likelihood

0.24%Up 0.2 points since Feb 10, 2026
90%50%10%1%

What each source reports

CVE List Score used 1.0

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

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.

Record
CVE-2026-23901
CVSS 4.0
1.0 LowCVSS: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
Weakness
CWE-208
Updated
2026-11-02
EUVDEUVD-2026-6879 1.0

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.

Record
EUVD-2026-6879
CVSS 4.0
1.0 LowCVSS: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
Updated
2026-11-02
GitHub AdvisoriesGHSA-c4qc-4q9p-m9q9 1.0

Apache Shiro Affected by an Observable Timing Discrepancy Vulnerability

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.

Record
GHSA-c4qc-4q9p-m9q9
CVSS 4.0
1.0 LowCVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:A/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N
Weakness
CWE-208
Updated
2026-11-02
NVD 1.0

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.

Record
CVE-2026-23901
CVSS 4.0
1.0 LowCVSS: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
CVSS 3.1
2.5 LowCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-208
Updated
2026-11-02
OSV 2.5

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.

Record
CVE-2026-23901
CVSS 3.1
2.5 LowCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
OSVDEBIAN-CVE-2026-23901 2.5

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.

Record
DEBIAN-CVE-2026-23901
CVSS 3.1
2.5 LowCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
OSVGHSA-c4qc-4q9p-m9q9 1.0

Apache Shiro Affected by an Observable Timing Discrepancy Vulnerability

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.

Record
GHSA-c4qc-4q9p-m9q9
CVSS 4.0
1.0 LowCVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:A/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N
Weakness
CWE-208
Updated
2026-11-02
OSVUBUNTU-CVE-2026-23901 1.0

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.

Record
UBUNTU-CVE-2026-23901
CVSS 4.0
1.0 LowCVSS: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
CVSS 3.1
2.5 LowCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
org.apache.shiro:shiro-core
Maven
before 2.1.0
2.1.0
shiro
Debian:12
All versions, plus listed versions
1.3.2-51.3.2-6
None known
shiro
Debian:13
All versions, plus listed versions
1.3.2-6
None known
shiro
Debian:14
All versions, plus listed versions
1.3.2-6
None known
org.apache.shiro:shiro-core
Maven
before 2.1.0, plus listed versions
1.0.0-incubating1.1.01.10.01.10.11.11.0
Show 37 moreShow less
1.12.01.13.01.2.01.2.11.2.21.2.31.2.41.2.51.2.61.3.01.3.11.3.21.4.01.4.0-RC21.4.11.4.21.5.01.5.11.5.21.5.31.6.01.7.01.7.11.8.01.9.01.9.12.0.02.0.0-alpha-12.0.0-alpha-22.0.0-alpha-32.0.0-alpha-42.0.12.0.22.0.32.0.42.0.52.0.6
2.1.0
shiro
Ubuntu:Pro:16.04:LTS
All versions, plus listed versions
1.2.4-11.2.4-1ubuntu0.1~esm11.2.4-1ubuntu0.1~esm2
None known
shiro
Ubuntu:Pro:18.04:LTS
All versions, plus listed versions
1.3.2-21.3.2-3~18.041.3.2-3~18.04.11.3.2-3ubuntu0.18.04.1~esm1
None known
shiro
Ubuntu:20.04:LTS
All versions, plus listed versions
1.3.2-41.3.2-4ubuntu0.11.3.2-4ubuntu0.2
None known
shiro
Ubuntu:22.04:LTS
All versions, plus listed versions
1.3.2-41.3.2-5
None known
shiro
Ubuntu:Pro:24.04:LTS
All versions, plus listed versions
1.3.2-51.3.2-5ubuntu0.24.04.1~esm1
None known
shiro
Ubuntu:25.10
All versions, plus listed versions
1.3.2-6ubuntu1
None known
shiro
Ubuntu:26.10
All versions, plus listed versions
1.3.2-6ubuntu2
None known
shiro
Ubuntu:26.04:LTS
All versions, plus listed versions
1.3.2-6ubuntu11.3.2-6ubuntu2
None known

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-23901 is a low vulnerability (CVSS 1.0) in Apache Shiro, published February 10, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.24%, the 15th percentile. Fixed in org.apache.shiro:shiro-core 2.1.0.

References

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