CVE-2026-23901
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.
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
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 Low
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 - 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 Low
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 - 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 Low
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 - 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 Low
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 - CVSS 3.1
- 2.5 Low
CVSS: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 Low
CVSS: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 Low
CVSS: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 Low
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 - 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 Low
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 - CVSS 3.1
- 2.5 Low
CVSS: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
| Package | Affected | Fixed |
|---|---|---|
org.apache.shiro:shiro-coreMaven |
before 2.1.0 | 2.1.0 |
shiroDebian:12 |
All versions, plus listed versions 1.3.2-51.3.2-6 |
None known |
shiroDebian:13 |
All versions, plus listed versions 1.3.2-6 |
None known |
shiroDebian:14 |
All versions, plus listed versions 1.3.2-6 |
None known |
org.apache.shiro:shiro-coreMaven |
before 2.1.0, plus listed versions 1.0.0-incubating1.1.01.10.01.10.11.11.0 Show 37 moreShow less1.12.01.13.01.2.01.2.11.2.21.2.31.2.41.2.51.2.61.3.01.3.11.3.21.4.01.4.0-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 |
shiroUbuntu: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 |
shiroUbuntu: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 |
shiroUbuntu:20.04:LTS |
All versions, plus listed versions 1.3.2-41.3.2-4ubuntu0.11.3.2-4ubuntu0.2 |
None known |
shiroUbuntu:22.04:LTS |
All versions, plus listed versions 1.3.2-41.3.2-5 |
None known |
shiroUbuntu:Pro:24.04:LTS |
All versions, plus listed versions 1.3.2-51.3.2-5ubuntu0.24.04.1~esm1 |
None known |
shiroUbuntu:25.10 |
All versions, plus listed versions 1.3.2-6ubuntu1 |
None known |
shiroUbuntu:26.10 |
All versions, plus listed versions 1.3.2-6ubuntu2 |
None known |
shiroUbuntu:26.04:LTS |
All versions, plus listed versions 1.3.2-6ubuntu11.3.2-6ubuntu2 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE 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
lists.apache.org/thread/mm1jct9b86jvnh3y44tj22xvjtx3xhhh
openwall.com/lists/oss-security/2026/02/08/2
nvd.nist.gov/vuln/detail/CVE-2026-23901
github.com/advisories/GHSA-c4qc-4q9p-m9q9
security-tracker.debian.org/tracker/CVE-2026-23901
github.com/apache/shiro
ubuntu.com/security/CVE-2026-23901
cve.org/CVERecord?id=CVE-2026-23901