Authentication Bypass in Apache Shiro shiro-guice
CVE-2026-56091 is an authentication bypass vulnerability in Apache Shiro when the shiro-guice module is used in a web servlet context. A specially crafted HTTP request can cause Shiro to incorrectly bypass authentication checks. The issue is described as similar to CVE-2020-1957, but affects shiro-guice rather than shiro-spring. Based on the provided information, affected versions include all Apache Shiro releases through the 2.x line and 3.0.0-alpha-1 when deployed with shiro-guice in a servlet-based web application.
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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 integration. This can permit unauthorized access to endpoints or functionality that should require prior authentication, with downstream impact dependent on the application’s authorization model and exposed resources.Mitigation
If you can’t patch tonight, do this now.
shiro-guice module in web servlet deployments, restricting access to affected applications, and placing additional authentication or access-control enforcement in front of sensitive endpoints where feasible. However, the provided content does not specify an official vendor mitigation other than upgrading.Remediation
Patch, then assume compromise.
shiro-guice in a web servlet context should be updated to a fixed release.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.