Unrated

Incomplete effective web.xml logging in Apache Tomcat

IdentifiersCVE-2026-55276CWE-670

CVE-2026-55276 is a low-severity vulnerability in Apache Tomcat caused by an always-incorrect control flow condition when generating the logged representation of the effective web.xml. As a result, special roles and empty authorization constraints are omitted from the logged effective web.xml, producing an incomplete record of the application’s effective security configuration. The issue affects 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, and 8.5.0 through 8.5.100. 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.

Successful triggering of this flaw does not, based on the provided information, directly grant code execution or privilege escalation. Its impact is on integrity and visibility of security-relevant logging and configuration auditing: administrators or defenders relying on the logged effective web.xml may see an incomplete view of configured security constraints because special roles and empty authorization constraints are missing from the log output. This can mislead review, troubleshooting, compliance validation, or forensic analysis of Tomcat security configuration.

Mitigation

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

If immediate upgrade is not possible, do not rely solely on the logged effective web.xml for validation of security constraints. Independently review the deployed web.xml and related effective security configuration through alternate administrative or deployment validation methods. However, the primary mitigation in the provided information is upgrade to a fixed release.

Remediation

Patch, then assume compromise.

Upgrade Apache Tomcat to a fixed version. Apache recommends upgrading to 11.0.23, 10.1.56, or 9.0.119, depending on the deployed branch. The provided notice states that 8.5.x versions through 8.5.100 are affected, but does not specify a fixed 8.5.x release in the supplied content. Unsupported end-of-life versions should be assumed potentially affected and migrated to a supported fixed branch.

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.

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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-2026-55276

NVD

nvd.nist.gov/vuln/detail/CVE-2026-55276

MITRE CWE · CWE-670

cwe.mitre.org