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Improper Authorization in Apache Tomcat Default Servlet Security Constraints

IdentifiersCVE-2026-55956CWE-285

CVE-2026-55956 is an improper authorization flaw in Apache Tomcat affecting the default servlet. When security constraints are defined for the default servlet, Tomcat incorrectly ignores any configured HTTP method restrictions or method omissions that are part of the constraint. As a result, authorization decisions for requests handled by the default servlet may not honor the administrator’s intended per-method access-control policy. 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.

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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 cause access-control rules on the default servlet to be applied incorrectly, allowing requests using HTTP methods that should have been restricted or excluded by configuration to bypass intended authorization checks. This can expose protected static resources or servlet-handled content via unauthorized methods, weakening application security policy and potentially enabling unauthorized access to data or functionality that administrators expected to be blocked for specific request methods.

Mitigation

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

If immediate upgrade is not possible, review and avoid relying on default-servlet security constraints that depend on HTTP method or method-omission semantics for protection. Enforce equivalent authorization controls elsewhere, such as at the application layer, in a front-end reverse proxy or WAF, or by restricting exposure of resources served by the default servlet until Tomcat can be upgraded. The provided information does not include an official vendor workaround beyond upgrading.

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. Users on affected older supported branches should move to the corresponding fixed version. Users on unsupported branches such as 8.5.x and 7.0.x should migrate to a supported fixed branch, as those branches are affected and no supported fix version for those lines is indicated in the provided content.
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

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

7 SOURCESView more in app

No news coverage yet. Advisories and community discussion only.

What this page doesn’t show

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Exposure mapping

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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 activity7

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