Unrated

Improper Authorization in Apache Tomcat Default Servlet Security Constraints

IdentifiersCVE-2026-55956CWE-285

CVE-2026-55956 is an improper authorization vulnerability in Apache Tomcat affecting the default servlet. When security constraints are specified for the default servlet, configured HTTP method restrictions or method-omission settings are ignored. As a result, authorization decisions for requests handled by the default servlet may not enforce the intended per-method access-control policy defined by the administrator. Affected versions are Tomcat 11.0.0-M1 through 11.0.22, 10.1.0-M1 through 10.1.55, 9.0.0.M1 through 9.0.118, 8.5.0 through 8.5.100, and 7.0.0 through 7.0.109. Other end-of-support versions may also be affected.

For your environment

Are you exposed to this one?

Mallory correlates every CVE against your assets, your vendors, and active adversary campaigns. Know which vulnerabilities matter for you, not just which ones are loud.

Start free trial

ANALYST BRIEF

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.

The flaw can undermine application or container-level access controls by allowing requests using HTTP methods that should have been restricted or excluded by security-constraint configuration on the default servlet. This may permit unauthorized access to resources served by the default servlet and bypass intended authorization policy for specific request methods. The available information does not indicate code execution or privilege escalation beyond authorization bypass.

Mitigation

If you can’t patch tonight, do this now.

If immediate upgrade is not possible, review and minimize reliance on HTTP method or method-omission restrictions in security constraints for resources served by the default servlet, since those controls may not be enforced as intended in affected versions. Restrict exposure of sensitive content through the default servlet where possible, and apply compensating controls such as upstream access-control enforcement at a reverse proxy or WAF. These are temporary mitigations only; vendor-recommended remediation is to upgrade.

Remediation

Patch, then assume compromise.

Upgrade Apache Tomcat to a fixed release. Apache states that the issue is fixed in Tomcat 11.0.23, 10.1.56, and 9.0.119. For older supported branches identified in the advisory, move to the latest fixed version available for the relevant supported branch. End-of-support versions should be upgraded to a supported release because they may also be affected and will not receive fixes.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

ACTIVITY FEED

Recent activity

8 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.

8 SOURCESView more in app

No news coverage yet. Advisories and community discussion only.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.

Start free trial

Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity8

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES

MITRE CVE

cve.org · CVE-2026-55956

NVD

nvd.nist.gov/vuln/detail/CVE-2026-55956

MITRE CWE · CWE-285

cwe.mitre.org