CVE-2026-41293Network attack vector

Unexpected application behavior via invalid HTTP/2 headers

Published May 12, 2026 · Updated May 12, 2026

Improper input validation in Apache Tomcat allows remote attackers to trigger unexpected application behavior via crafted HTTP/2 headers. The HPACK decoder accepted invalid field-name and field-value characters in literal and Huffman-encoded headers, then exposed those values through the Servlet API. Reachability requires HTTP/2 processing and an application that assumes Servlet API header values comply with the specification; Apache reports no HTTP/2 request-smuggling concern.

CVSS severity9.8
Critical
EPSS probability1.68%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Apache Tomcat allows remote attackers to trigger unexpected application behavior via crafted HTTP/2 headers. The HPACK decoder accepted invalid field-name and field-value characters in literal and Huffman-encoded headers, then exposed those values through the Servlet API. Reachability requires HTTP/2 processing and an application that assumes Servlet API header values comply with the specification; Apache reports no HTTP/2 request-smuggling concern.

The record

CVE
CVE-2026-41293
Published
May 12, 2026
Updated
May 12, 2026
Vendor
The Apache Software Foundation
Product
Apache Tomcat
Classifications
CWE-20
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 12, 2026CVE publishedPublication date reported by the CVE source.
  2. May 12, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.0.0-M1 <=10.0.27
  2. Affected versionversion=10.1.0-M1 <=10.1.54
  3. Affected versionversion=11.0.0-M1 <=11.0.21
  4. Affected versionversion=8.5.0 <=8.5.100
  5. Affected versionversion=9.0.0.M1 <=9.0.117

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache Tomcatversion=10.0.0-M1 <=10.0.27; version=10.1.0-M1 <=10.1.54; version=11.0.0-M1 <=11.0.21; version=8.5.0 <=8.5.100; version=9.0.0.M1 <=9.0.117

Published CVSS scores

9.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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