Apache Tomcat: HTTP/2 DoS via malformed request

Answer in brief

CVE-2026-78437 records a Unknown severity vulnerability in Apache Tomcat: HTTP/2 DoS via malformed request. The current sources do not mark it as known exploited. The current feed maps Apache Software Foundation/Apache Tomcat (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 23, 2026Updated Sep 23, 2026Source checked Sep 23, 2026First seen by HOL Sep 23, 2026Material review Sep 23, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Not reported

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Apache Software Foundation/Apache Tomcat (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Apache Software Foundation/Apache Tomcatgeneric	>=11.0.19 <=11.0.25 \|\| >=10.1.53 <=10.1.59 \|\| >=9.0.116 <=9.0.121	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Apache Software Foundation/Apache Tomcat.
Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

Published upstream
Sep 23, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 23, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 23, 2026

Sources and claim methodology

Source referencelists.apache.org

Upstream source description

Incomplete cleanup vulnerability in Apache Tomcat allows a malformed request to potentially (depends on timing) cause one request from another user to fail. This issue affects Apache Tomcat: from 11.0.19 through 11.0.25, from 10.1.53 through 10.1.59, from 9.0.116 through 9.0.121. Users are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue.

Quoted source text, attributed separately from HOL analysis.