Undertow-core: undertow: denial of service via websocket permessage-deflate processing
Red Hat · Red Hat build of Apache Camel for Spring Boot 4
7.5HighCVSS 3.1
Recommended action
Within 7 days
High technical severity; prioritise exposed affected systems while verifying vendor guidance.
Mitigation available
Distribution package intelligence
Ubuntu vendor package status
Canonical’s release and source-package findings are shown separately from local repository availability.
1 package state
Repository candidate not checked
A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.
Ubuntu release
Source package
Vendor state
Fixed version
Evidence
Ubuntu 24.04 LTSnoble · esm-apps
undertow
Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.
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-2026-5680 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityundertow-core: Undertow: Denial of Service via WebSocket permessage-deflate processing
14 known affected
The vendor explicitly identifies these products as affected by this CVE.
undertow-core as a component of Red Hat build of Apache Camel for Spring Boot 4
undertow-core as a component of Red Hat Data Grid 8
pki-resteasy as a component of Red Hat Enterprise Linux 9
pki-resteasy-client as a component of Red Hat Enterprise Linux 9
pki-resteasy-core as a component of Red Hat Enterprise Linux 9
pki-resteasy-jackson2-provider as a component of Red Hat Enterprise Linux 9
pki-resteasy-servlet-initializer as a component of Red Hat Enterprise Linux 9
undertow-core as a component of Red Hat JBoss Enterprise Application Platform 7
undertow-core as a component of Red Hat JBoss Enterprise Application Platform 8
undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform 8
undertow-core as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack
undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack
Summary
A flaw was found in Undertow. A remote attacker could exploit this vulnerability by sending specially crafted WebSocket messages with permessage-deflate negotiated. This could lead to excessive memory consumption due to the PerMessageDeflateFunction.largerBuffer() method using exponential doubling, resulting in a Denial of Service (DoS) for the affected application.
Remediation
To mitigate this issue, configure the PerMessageDeflateHandshake to limit the maximum decompressed buffer size. This can be achieved by setting the maxDecompressedBufferSize parameter to a reasonable value (e.g., 10 MB) in the PerMessageDeflateHandshake constructor. This action may require a restart of the affected application or service to take effect.
Optional official sources
National CERT insights ?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.
Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.
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-2026-67086
No EUVD known-exploited evidence
A flaw was found in Undertow. A remote attacker could exploit this vulnerability by sending specially crafted WebSocket messages with permessage-deflate negotiated. This could lead to excessive memory consumption due to the PerMessageDeflateFunction.largerBuffer() method using exponential doubling, resulting in a Denial of Service (DoS) for the affected application.
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
7.5 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days
High technical severity; prioritise exposed affected systems while verifying vendor guidance.
Mitigation available
01
What, why and how
A flaw was found in Undertow. A remote attacker could exploit this vulnerability by sending specially crafted WebSocket messages with permessage-deflate negotiated. This could lead to excessive memory consumption due to the PerMessageDeflateFunction.largerBuffer() method using exponential doubling, resulting in a Denial of Service (DoS) for the affected application.
What
A flaw was found in Undertow. A remote attacker could exploit this vulnerability by sending specially crafted WebSocket messages with permessage-deflate negotiated. This could lead to excessive memory consumption due to the PerMessageDeflateFunction.largerBuffer() method using exponential doubling, resulting in a Denial of Service (DoS) for the affected application.
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 flaw was found in Undertow. A remote attacker could exploit this vulnerability by sending specially crafted WebSocket messages with permessage-deflate negotiated. This could lead to excessive memory consumption due to the PerMessageDeflateFunction.largerBuffer() method using exponential doubling, resulting in a Denial of Service (DoS) for the affected application.
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: 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.
ENISA EUVD · EUVD-2026-67086Official EUVD mapping
A flaw was found in Undertow. A remote attacker could exploit this vulnerability by sending specially crafted WebSocket messages with permessage-deflate negotiated. This could lead to excessive memory consumption due to the PerMessageDeflateFunction.largerBuffer() method using exponential doubling, resulting in a Denial of Service (DoS) for the affected application.
Official EUVD recordBSI · German · WID-SEC-W-2026-3059Red Hat Undertow: Schwachstelle ermöglicht Denial of Service
Ein entfernter, anonymer Angreifer kann eine Schwachstelle in Red Hat Undertow ausnutzen, um einen Denial of Service Angriff durchzuführen.
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.
Mitigation available
Affected
undertow-core as a component of Red Hat build of Apache Camel for Spring Boot 4; undertow-core as a component of Red Hat Data Grid 8; pki-resteasy as a component of Red Hat Enterprise Linux 9; pki-resteasy-client as a component of Red Hat Enterprise Linux 9; pki-resteasy-core as a component of Red Hat Enterprise Linux 9; pki-resteasy-jackson2-provider as a component of Red Hat Enterprise Linux 9; pki-resteasy-servlet-initializer as a component of Red Hat Enterprise Linux 9; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 7; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core as a component of Red Hat Process Automation 7; undertow-core as a component of Red Hat Single Sign-On 7
Fixed
No fixed version is explicitly recorded in the structured CVE data.
Action
No verified patch reference is present in the current structured sources. Check the vendor advisory before making a change.
Workaround
To mitigate this issue, configure the PerMessageDeflateHandshake to limit the maximum decompressed buffer size. This can be achieved by setting the maxDecompressedBufferSize parameter to a reasonable value (e.g., 10 MB) in the PerMessageDeflateHandshake constructor. This action may require a restart of the affected application or service to take effect.
04
Evidence and provenance
Published 27 Aug 2026 · Last source change 9 Sept 2026, 11:34 UTC · CWE-770 · Allocation of Resources Without Limits or Throttling
CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source ?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.FIRST · tracked since 2026-08-28
European sourceENISA EUVD · EUVD-2026-67086
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD awaiting enrichment
Core structured fields are present and their contributing authorities are shown above.
Affected versionsThe structured affected or fixed version information changed.
Before
undertow-core as a component of Red Hat build of Apache Camel for Spring Boot 4; undertow-core as a component of Red Hat Data Grid 8; resteasy-javadoc (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; resteasy.src (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; resteasy (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; pki-resteasy as a component of Red Hat Enterprise Linux 9; pki-resteasy-client as a component of Red Hat Enterprise Linux 9; pki-resteasy-core as a component of Red Hat Enterprise Linux 9; pki-resteasy-jackson2-provider as a component of Red Hat Enterprise Linux 9; pki-resteasy-servlet-initializer as a component of Red Hat Enterprise Linux 9; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 7; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core as a component of Red Hat Process Automation 7; undertow-core as a component of Red Hat Single Sign-On 7
After
undertow-core as a component of Red Hat build of Apache Camel for Spring Boot 4; undertow-core as a component of Red Hat Data Grid 8; pki-resteasy as a component of Red Hat Enterprise Linux 9; pki-resteasy-client as a component of Red Hat Enterprise Linux 9; pki-resteasy-core as a component of Red Hat Enterprise Linux 9; pki-resteasy-jackson2-provider as a component of Red Hat Enterprise Linux 9; pki-resteasy-servlet-initializer as a component of Red Hat Enterprise Linux 9; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 7; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core as a component of Red Hat Process Automation 7; undertow-core as a component of Red Hat Single Sign-On 7
Affected versionsThe structured affected or fixed version information changed.
Before
undertow-core as a component of Red Hat build of Apache Camel for Spring Boot 4; undertow-core as a component of Red Hat Data Grid 8; resteasy-javadoc (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; resteasy.src (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; resteasy (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; pki-resteasy as a component of Red Hat Enterprise Linux 9; pki-resteasy-client as a component of Red Hat Enterprise Linux 9; pki-resteasy-core as a component of Red Hat Enterprise Linux 9; pki-resteasy-jackson2-provider as a component of Red Hat Enterprise Linux 9; pki-resteasy-servlet-initializer as a component of Red Hat Enterprise Linux 9; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 7; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.18.Final.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.23.SP3-redhat-00001.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core as a component of Red Hat Process Automation 7; undertow-core as a component of Red Hat Single Sign-On 7
After
undertow-core as a component of Red Hat build of Apache Camel for Spring Boot 4; undertow-core as a component of Red Hat Data Grid 8; resteasy-javadoc (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; resteasy.src (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; resteasy (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; pki-resteasy as a component of Red Hat Enterprise Linux 9; pki-resteasy-client as a component of Red Hat Enterprise Linux 9; pki-resteasy-core as a component of Red Hat Enterprise Linux 9; pki-resteasy-jackson2-provider as a component of Red Hat Enterprise Linux 9; pki-resteasy-servlet-initializer as a component of Red Hat Enterprise Linux 9; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 7; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core as a component of Red Hat Process Automation 7; undertow-core as a component of Red Hat Single Sign-On 7
Affected versionsThe structured affected or fixed version information changed.
Before
undertow-core as a component of Red Hat build of Apache Camel for Spring Boot 4; undertow-core as a component of Red Hat Data Grid 8; resteasy-javadoc (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; resteasy.src (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; resteasy (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; pki-resteasy as a component of Red Hat Enterprise Linux 9; pki-resteasy-client as a component of Red Hat Enterprise Linux 9; pki-resteasy-core as a component of Red Hat Enterprise Linux 9; pki-resteasy-jackson2-provider as a component of Red Hat Enterprise Linux 9; pki-resteasy-servlet-initializer as a component of Red Hat Enterprise Linux 9; undertow-core as a component of Red Hat Fuse 7; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 7; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.18.Final.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.23.SP3-redhat-00001.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core as a component of Red Hat Process Automation 7; undertow-core as a component of Red Hat Single Sign-On 7
After
undertow-core as a component of Red Hat build of Apache Camel for Spring Boot 4; undertow-core as a component of Red Hat Data Grid 8; resteasy-javadoc (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; resteasy.src (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; resteasy (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; pki-resteasy as a component of Red Hat Enterprise Linux 9; pki-resteasy-client as a component of Red Hat Enterprise Linux 9; pki-resteasy-core as a component of Red Hat Enterprise Linux 9; pki-resteasy-jackson2-provider as a component of Red Hat Enterprise Linux 9; pki-resteasy-servlet-initializer as a component of Red Hat Enterprise Linux 9; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 7; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.18.Final.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.23.SP3-redhat-00001.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core as a component of Red Hat Process Automation 7; undertow-core as a component of Red Hat Single Sign-On 7
Affected versionsThe structured affected or fixed version information changed.
Before
undertow-core as a component of Red Hat build of Apache Camel for Spring Boot 4; undertow-core as a component of Red Hat Data Grid 8; moditect-javadoc as a component of Red Hat Enterprise Linux 10; moditect.src as a component of Red Hat Enterprise Linux 10; resteasy-javadoc (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; resteasy.src (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; resteasy (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; pki-resteasy as a component of Red Hat Enterprise Linux 9; pki-resteasy-client as a component of Red Hat Enterprise Linux 9; pki-resteasy-core as a component of Red Hat Enterprise Linux 9; pki-resteasy-jackson2-provider as a component of Red Hat Enterprise Linux 9; pki-resteasy-servlet-initializer as a component of Red Hat Enterprise Linux 9; undertow-core as a component of Red Hat Fuse 7; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 7; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.18.Final.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.23.SP3-redhat-00001.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core as a component of Red Hat Process Automation 7; undertow-core as a component of Red Hat Single Sign-On 7
After
undertow-core as a component of Red Hat build of Apache Camel for Spring Boot 4; undertow-core as a component of Red Hat Data Grid 8; resteasy-javadoc (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; resteasy.src (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; resteasy (pki-core:10.6) as a component of Red Hat Enterprise Linux 8; pki-resteasy as a component of Red Hat Enterprise Linux 9; pki-resteasy-client as a component of Red Hat Enterprise Linux 9; pki-resteasy-core as a component of Red Hat Enterprise Linux 9; pki-resteasy-jackson2-provider as a component of Red Hat Enterprise Linux 9; pki-resteasy-servlet-initializer as a component of Red Hat Enterprise Linux 9; undertow-core as a component of Red Hat Fuse 7; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 7; undertow-core as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform 8; undertow-core as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.10.Final.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.18.Final.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core-2.3.23.SP3-redhat-00001.jar as a component of Red Hat JBoss Enterprise Application Platform Expansion Pack; undertow-core as a component of Red Hat Process Automation 7; undertow-core as a component of Red Hat Single Sign-On 7
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.
CVE-2026-5680: Undertow-core: undertow: denial of service via websocket permessage-deflate processing | BlackTree
