Authentication Bypass in Apache Shiro shiro-guice Web Servlet Context
CVE-2026-56091 is an authentication bypass vulnerability in Apache Shiro's shiro-guice module when it is deployed in a web servlet context. According to the provided advisory text, a specially crafted HTTP request can cause authentication checks to be bypassed. The issue is described as similar to CVE-2020-1957, but affects shiro-guice rather than shiro-spring. The vulnerability affects all Apache Shiro versions through the 2.x line and also 3.0.0-alpha-1 when the shiro-guice module is in use in a web servlet deployment.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
shiro-guice web servlet integrations. This can permit access to resources or application functionality that should require prior authentication. The precise downstream impact depends on the protected application, but may include unauthorized access to sensitive data and authenticated-only operations.Mitigation
If you can’t patch tonight, do this now.
shiro-guice module in a web servlet context until a fixed version can be deployed. Restrict external access to affected applications where feasible and place compensating access controls in front of vulnerable endpoints. However, the provided content identifies upgrading to 3.0.0 or later as the definitive fix.Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Recent activity
6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An authentication bypass vulnerability in Apache Shiro's shiro-guice module when used in a web servlet context, triggered by a specially crafted HTTP request.
An authentication bypass vulnerability in Apache Shiro's shiro-guice module when used in a web servlet context, triggered by a specially crafted HTTP request.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.