CVE-2026-54428Network attack vector

Denial of service via unlimited pre-ACK HPACK decoding

Published Jul 1, 2026 · Updated Jul 1, 2026

Uncontrolled resource consumption in Apache HttpComponents Core 5.4.2 and earlier and 5.5-beta1 and earlier allows remote attackers to exhaust memory. The AbstractH2StreamMultiplexer initializes HPackDecoder.maxListSize with HTTP/2's unlimited initial value instead of the configured local header-list limit, leaving compressed headers unbounded until SETTINGS is acknowledged. An unauthenticated remote peer can send an oversized compressed header block during that pre-acknowledgement window and interrupt the embedding service through memory exhaustion.

CVSS severity7.5
High
EPSS probability0.87%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled resource consumption in Apache HttpComponents Core 5.4.2 and earlier and 5.5-beta1 and earlier allows remote attackers to exhaust memory. The AbstractH2StreamMultiplexer initializes HPackDecoder.maxListSize with HTTP/2's unlimited initial value instead of the configured local header-list limit, leaving compressed headers unbounded until SETTINGS is acknowledged. An unauthenticated remote peer can send an oversized compressed header block during that pre-acknowledgement window and interrupt the embedding service through memory exhaustion.

The record

CVE
CVE-2026-54428
Published
Jul 1, 2026
Updated
Jul 1, 2026
Vendor
The Apache Software Foundation
Product
Apache HttpComponents Core
Classifications
CWE-400, CWE-770, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 1, 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=5.0-alpha <=5.4.2
  2. Affected versionversion=5.5-alpha <=5.5-beta1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache HttpComponents Coreversion=5.0-alpha <=5.4.2; version=5.5-alpha <=5.5-beta1

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-400Uncontrolled Resource Consumption
CWE-770Allocation of Resources Without Limits or Throttling
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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