CVE-2026-23903VulnerabilityPublished 9 Feb 2026Updated 20 Aug 2026

CVE-2026-23903: Apache Shiro · Authentication Bypass by Alternate Name

Affects Apache ShiroSource CVE Database V5

Not known to be exploited · CVSS 5.3 Medium : upgrade to 2.0.7 when convenient.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 34% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.0.7

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 9 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Apache to 2.0.7.

Affected software

Product	Affected	Fixed in
Apache Software FoundationApache Shiro	Affected <2.0.7	Fixed in 2.0.7
MavenApache Software Foundation/org.apache.shiro:shiro-web`pkg:maven/Apache Software Foundation/org.apache.shiro:shiro-web`Other threats	Affected <2.0.7	Fixed in 2.0.7

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should immediately upgrade Apache Shiro to version 2.0.7 or later to remediate this vulnerability. For environments where immediate upgrade is not feasible, configure the new parameters to enforce case sensitivity in filtering: set 'filterChainResolver.caseInsensitive = true' in shiro.ini or 'shiro.caseInsensitive=true' in application.properties to ensure proper handling of case variations. Conduct an audit of static file serving configurations to identify any sensitive files that may be exposed due to case-insensitive filesystem behavior. Implement strict access controls and consider serving static files from case-sensitive filesystems or using web server configurations that enforce case sensitivity. Monitor web server logs for unusual access patterns involving case variations in filenames. Additionally, integrate this vulnerability into vulnerability management and patching workflows to ensure timely updates. Educate development and operations teams about the importance of case sensitivity in security filtering.

Description

Authentication Bypass by Alternate Name vulnerability in Apache Shiro. This issue affects Apache Shiro: before 2.0.7. Users are recommended to upgrade to version 2.0.7, which fixes the issue. The issue only effects static files. If static files are served from a case-insensitive filesystem, such as default macOS setup, static files may be accessed by varying the case of the filename in the request. If only lower-case (common default) filters are present in Shiro, they may be bypassed this way. Shiro 2.1.0 and later has a new parameters to remediate this issue shiro.ini: filterChainResolver.caseInsensitive = true application.properties: shiro.caseInsensitive=true Shiro 3.0.0 and later makes this the default in shiro.ini-based configurations. Shiro 3.0.1 and later makes this the default in all configurations, including programmatic and Spring / Spring Boot.

Impact

For European organizations, this vulnerability could lead to unauthorized access to sensitive static files served by applications using vulnerable Apache Shiro versions on case-insensitive filesystems. While the impact is limited to confidentiality and does not affect integrity or availability, exposure of static resources could include sensitive configuration files, documentation, or other data that may aid further attacks or leak sensitive information. Organizations in sectors with strict data protection regulations (e.g., GDPR) could face compliance risks if sensitive data is exposed. The risk is higher for organizations using macOS or other case-insensitive filesystems in their deployment environments. Since the vulnerability does not require authentication or user interaction, it can be exploited by remote attackers, increasing the threat surface. However, the absence of known exploits in the wild reduces immediate risk, though proactive mitigation is essential to prevent future exploitation.

Summary

CVE-2026-23903 is a medium-severity authentication bypass vulnerability in the Apache Shiro framework affecting versions before 2.0.7. The issue arises from how Shiro handles static file requests on case-insensitive filesystems, such as the default macOS setup. When static files are served, Shiro applies filters to restrict access, commonly using lower-case filters. However, due to case insensitivity at the filesystem level, an attacker can vary the case of the filename in the HTTP request to bypass these filters, effectively circumventing authentication controls intended to protect static resources. This vulnerability is classified under CWE-289 (Authentication Bypass). The flaw does not require authentication or user interaction and can be exploited remotely over the network. The impact is limited to confidentiality as unauthorized users may access static files that should be protected. Apache Shiro 2.0.7 addresses this by introducing configuration options (filterChainResolver.caseInsensitive and shiro.caseInsensitive) to properly handle case sensitivity in filtering. The upcoming 3.0.0 release will enable case-insensitive filtering by default, further securing static file access. No known exploits are currently reported in the wild, but the vulnerability is publicly disclosed and should be mitigated promptly.

CWE-289Authentication Bypass by Alternate Name (opens in a new tab)
Base weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The product performs authentication based on the name of a resource being accessed, or the name of the actor performing the access, but it does not properly check all possible names for that resource or actor.
Architecture and Design · Input Validation
Avoid making decisions based on names of resources (e.g. files) if those resources can have alternate names.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Implementation · Input Validation
Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174).
OWASP Cheat Sheets
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V2.8.5 (opens in a new tab)
V2.8.4 (opens in a new tab)
V9.2.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 16 Feb 2026, 13:23 UTC

WeaknessesCWE-289

Technical details

References

Community reviews

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