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Full vulnerability report · 2026
CVE-2026-66257High confidence

Apache Qpid Proton-J: Unbounded symbol value caching can lead to pre-authentication resource exhaustion

Apache Software Foundation · Apache Qpid Proton-J

7.5HighCVSS 3.1
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:High, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 0.77% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Apache Software Foundation Apache Qpid Proton-J and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 30 daysRemediation target: Within 180 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2026-66257 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityqpid-proton-j: Apache Qpid Proton-J: Denial of Service via unbounded symbol value caching
2 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • proton-j as a component of Red Hat build of Apache Camel 4 for Quarkus 3
  • proton-j as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack
Summary
A flaw was found in Apache Qpid Proton-J. A remote attacker, without needing to authenticate, could exploit an issue with unbounded symbol value caching. This could lead to resource exhaustion, where the system runs out of available resources, ultimately causing a denial of service (DoS). A denial of service attack makes the affected system unavailable to legitimate users.
Remediation
Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-53051

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

A pre-authentication attacker could leverage unbounded symbol value caching to cause resource exhaustion leading to denial of service. This issue affects Apache Qpid Proton-J: through 0.34.1. Users are recommended to upgrade to version 0.35.0, which fixes the issue.

What

A pre-authentication attacker could leverage unbounded symbol value caching to cause resource exhaustion leading to denial of service. This issue affects Apache Qpid Proton-J: through 0.34.1. Users are recommended to upgrade to version 0.35.0, which fixes the issue.

Why

The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

What

A pre-authentication attacker could leverage unbounded symbol value caching to cause resource exhaustion leading to denial of service. This issue affects Apache Qpid Proton-J: through 0.34.1. Users are recommended to upgrade to version 0.35.0, which fixes the issue.

Why

The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Allocation of Resources Without Limits or Throttling → disrupt the affected service
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-770 ↗

CWE-770: Allocation of Resources Without Limits or Throttling. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedDenial of serviceCWE-770
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

Cyber Security Agency of Singapore · English · CSA-SB-20260812Security Bulletin 12 Aug 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 12 Aug 2026, published on 12 August 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-027524Apache Software FoundationのQpid Proton-Jにおける制限またはスロットリング無しのリソースの割り当てに関する脆弱性

認証前の攻撃者が無制限のシンボル値キャッシュを悪用することでリソースが枯渇し、サービス拒否（DoS）状態を引き起こす可能性があります。この問題はApache Qpid Proton-J バージョン0.34.1までに影響します。ユーザーはこの問題を修正したバージョン0.35.0へアップグレードすることを推奨します。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
Fixed
Action
Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 5 Aug 2026 · Last source change 6 Aug 2026, 13:13 UTC · CWE-770 · Allocation of Resources Without Limits or Throttling

CVE recordCVE.org · 5.2
CVSS sourceCISA ADP
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-53051
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    proton-j as a component of Red Hat build of Apache Camel 4 for Quarkus 3; proton-j as a component of Red Hat build of Apache Camel for Spring Boot 4; proton-j as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack · Fixed: AMQ Clients 2026.Q3; Red Hat AMQ Broker 7.13.6; Red Hat AMQ Broker 7.14.1
    After
    proton-j as a component of Red Hat build of Apache Camel 4 for Quarkus 3; proton-j as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack · Fixed: AMQ Clients 2026.Q3; Red Hat AMQ Broker 7.13.6; Red Hat AMQ Broker 7.14.1; Red Hat build of Apache Camel 4.18.4 for Spring Boot 3.5.16
    Red Hat Product Security ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    ≤ 0.34.1 · Fixed: Before applying the update, back up your existing installation, including all applications, configuration files, databases and database settings. The References section of this erratum contains a download link (you must log in to download the update).
    After
    ≤ 0.34.1 · Fixed: Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
    Red Hat Product Security ↗
  3. Vendor guidanceAuthoritative vendor guidance changed from remediation: access.redhat.com/CVE-2026-66257 to remediation: access.redhat.com/CVE-2026-66257.
    Before
    remediation: access.redhat.com/CVE-2026-66257
    After
    remediation: access.redhat.com/CVE-2026-66257
    Red Hat Product Security ↗
  4. Affected versionsThe structured affected or fixed version information changed.
    Before
    proton-j as a component of Red Hat AMQ Clients; proton-j as a component of Red Hat build of Apache Camel 4 for Quarkus 3; proton-j as a component of Red Hat build of Apache Camel for Spring Boot 4; proton-j as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack · Fixed: Red Hat AMQ Broker 7.13.6; Red Hat AMQ Broker 7.14.1
    After
    proton-j as a component of Red Hat build of Apache Camel 4 for Quarkus 3; proton-j as a component of Red Hat build of Apache Camel for Spring Boot 4; proton-j as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack · Fixed: AMQ Clients 2026.Q3; Red Hat AMQ Broker 7.13.6; Red Hat AMQ Broker 7.14.1
    Red Hat Product Security ↗
  5. Affected versionsThe structured affected or fixed version information changed.
    Before
    ≤ 0.34.1 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    ≤ 0.34.1 · Fixed: Before applying the update, back up your existing installation, including all applications, configuration files, databases and database settings. The References section of this erratum contains a download link (you must log in to download the update).
    Red Hat Product Security ↗
  6. Remediation statusRemediation status changed from Awaiting fix to Patch available.
    Before
    Awaiting fix
    After
    Patch available
    Red Hat Product Security ↗
  7. Affected versionsThe structured affected or fixed version information changed.
    Before
    proton-j as a component of Red Hat AMQ Clients; proton-j as a component of Red Hat build of Apache Camel 4 for Quarkus 3; proton-j as a component of Red Hat build of Apache Camel for Spring Boot 4; proton-j as a component of Red Hat build of Quarkus; proton-j as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack · Fixed: Red Hat AMQ Broker 7.13.6; Red Hat AMQ Broker 7.14.1; Red Hat Build of Apache Camel 3.33 for Quarkus 3.33.3.SP1
    After
    proton-j as a component of Red Hat AMQ Clients; proton-j as a component of Red Hat build of Apache Camel 4 for Quarkus 3; proton-j as a component of Red Hat build of Apache Camel for Spring Boot 4; proton-j as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack · Fixed: Red Hat AMQ Broker 7.13.6; Red Hat AMQ Broker 7.14.1
    Red Hat Product Security ↗
  8. Vendor guidanceAuthoritative vendor guidance changed from remediation: access.redhat.com/CVE-2026-66257 to remediation: access.redhat.com/CVE-2026-66257.
    Before
    remediation: access.redhat.com/CVE-2026-66257
    After
    remediation: access.redhat.com/CVE-2026-66257
    Red Hat Product Security ↗
  9. Remediation statusRemediation status changed from Mitigation available to Patch available.
    Before
    Mitigation available
    After
    Patch available
    Red Hat Product Security ↗
  10. Affected versionsThe structured affected or fixed version information changed.
    Before
    proton-j as a component of Red Hat AMQ Broker 7; proton-j as a component of Red Hat AMQ Clients; proton-j as a component of Red Hat build of Apache Camel 4 for Quarkus 3; proton-j as a component of Red Hat build of Apache Camel for Spring Boot 4; proton-j as a component of Red Hat build of Quarkus; proton-j as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack
    After
    proton-j as a component of Red Hat AMQ Clients; proton-j as a component of Red Hat build of Apache Camel 4 for Quarkus 3; proton-j as a component of Red Hat build of Apache Camel for Spring Boot 4; proton-j as a component of Red Hat build of Quarkus; proton-j as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack · Fixed: Red Hat AMQ Broker 7.13.6; Red Hat AMQ Broker 7.14.1; Red Hat Build of Apache Camel 3.33 for Quarkus 3.33.3.SP1
    Red Hat Product Security ↗
  11. Vendor guidanceAuthoritative vendor guidance changed from remediation: access.redhat.com/CVE-2026-66257 to remediation: access.redhat.com/CVE-2026-66257.
    Before
    remediation: access.redhat.com/CVE-2026-66257
    After
    remediation: access.redhat.com/CVE-2026-66257
    Red Hat Product Security ↗
  12. Remediation statusRemediation status changed from Awaiting fix to Mitigation available.
    Before
    Awaiting fix
    After
    Mitigation available
    Red Hat Product Security ↗
  13. Affected versionsThe structured affected or fixed version information changed.
    Before
    proton-j as a component of Red Hat AMQ Broker 7
    After
    proton-j as a component of Red Hat AMQ Broker 7; proton-j as a component of Red Hat AMQ Clients; proton-j as a component of Red Hat build of Apache Camel 4 for Quarkus 3; proton-j as a component of Red Hat build of Apache Camel for Spring Boot 4; proton-j as a component of Red Hat build of Quarkus; proton-j as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack
    Red Hat Product Security ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release recorded from official guidance
Fixed release recorded from official guidance
Fixed release recorded from official guidance
ENISA EUVD · EUVD-2026-53051↗Red Hat Product Security security advisory↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-66257 · cve.blacktree.nl