CVE-2026-66257Network attack vectorHinoki check available

Pre-authentication service interruption via unbounded symbol caching

Published Aug 5, 2026 · Updated Aug 5, 2026

Resource exhaustion in Apache Qpid Proton-J 0.34.1 and earlier allows remote attackers to interrupt AMQP services before authentication. The library caches distinct symbol values supplied by an AMQP peer without a size or entry limit; Apache has not identified the implementing class or method. Any network-facing application that decodes unauthenticated AMQP traffic with the library is exposed to process degradation or termination.

CVSS severity7.5
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Resource exhaustion in Apache Qpid Proton-J 0.34.1 and earlier allows remote attackers to interrupt AMQP services before authentication. The library caches distinct symbol values supplied by an AMQP peer without a size or entry limit; Apache has not identified the implementing class or method. Any network-facing application that decodes unauthenticated AMQP traffic with the library is exposed to process degradation or termination.

The record

CVE
CVE-2026-66257
Published
Aug 5, 2026
Updated
Aug 5, 2026
Vendor
The Apache Software Foundation
Product
Apache Qpid Proton-J
Classifications
CWE-770, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 5, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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=0 <=0.34.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache Qpid Proton-Jversion=0 <=0.34.1

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.

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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-770Allocation of Resources Without Limits or Throttling
T1499Endpoint Denial of Service

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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