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FuseApplication · Redhat

CVE-2021-3597

MEDIUM · 5.9 CVSS v3.1 Published 2022-05-24
Fix available
A fix is available. Upgrade to 2.0.35 / 2.2.6 or later.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A flaw was found in undertow. The HTTP2SourceChannel fails to write the final frame under some circumstances, resulting in a denial of service. The highest threat from this vulnerability is availability. This flaw affects Undertow versions prior to 2.0.35.SP1, prior to 2.2.6.SP1, prior to 2.2.7.SP1, prior to 2.0.36.SP1, prior to 2.2.9.Final and prior to 2.0.39.Final.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A flaw in the HTTP2SourceChannel of Undertow causes failure to write the final HTTP/2 frame under certain conditions, leading to a denial of service condition. The vulnerability affects HTTP/2 connection handling where the final frame (likely a GOAWAY or window update) is not properly transmitted, potentially hanging connections.

MitigationUpgrade Undertow to version 2.0.35.SP1 or later for 2.0.x branches, or 2.2.6.SP1/2.2.9.Final or later for 2.2.x branches. For 2.0.x, upgrade to 2.0.36.SP1 or 2.0.39.Final. Ensure HTTP/2 functionality is tested after upgrade.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FuseApplication
Affected:= 1.0
Jboss Enterprise Application PlatformApplication
Affected:all versions= 7.3= 7.4
Openshift Application RuntimesApplication
Affected:all versions
Single Sign OnApplication
Affected:all versions
UndertowApplication
Affected:< 2.0.35>= 2.2.0, < 2.2.6= 2.0.35= 2.0.36= 2.0.39= 2.2.6= 2.2.7= 2.2.9
Active Iq Unified ManagerApplication
Affected:all versions
Oncommand InsightApplication
Affected:all versions
Oncommand Workflow AutomationApplication
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Undertow installation
    Search for undertow-core JAR files in your application lib directories, or grep for 'undertow-core' in pom.xml/build.gradle dependency files. Check JBoss/Wildfly modules for undertow subystem.
    Affected if Undertow is present in the environment
  2. Determine Undertow version
    For JAR-based deployments: examine the filename of undertow-core (e.g., undertow-core-2.0.33.jar). For JBoss/Wildfly: check the version in module.xml or run 'twiddle.sh info jboss.as:subsystem=undertow' if available. Check Maven dependency tree for undertow version.
    Affected if Version is < 2.0.35, or = 2.0.35/2.0.36/2.0.39, or >= 2.2.0 and < 2.2.6, or = 2.2.6/2.2.7/2.2.9
  3. Verify HTTP/2 is enabled
    Check server configuration files (standalone.xml/standalone-ha.xml for JBoss, undertow.xml, or Spring Boot application.properties) for HTTP/2 connector configuration. Look for 'upgrade-to-http2' or 'http2' in listener/connector settings.
    Affected if HTTP/2 protocol handling is enabled on any Undertow listener
  4. Check for connection hang symptoms
    Monitor for stuck HTTP/2 connections that never complete. Review server logs for 'Connection closed unexpectedly' or timeout errors. Use network captures to verify final HTTP/2 frames (GOAWAY, WINDOW_UPDATE) are not being sent to clients.
    Affected if HTTP/2 connections hang or timeout without proper response completion

Affected if Undertow version is in the vulnerable range AND HTTP/2 is enabled and connections exhibit hanging behavior.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2.0.35 / 2.2.6 or later
Fixed in 2.0.352.2.6
Interim mitigation

Upgrade Undertow to version 2.0.35.SP1 or later for 2.0.x branches, or 2.2.6.SP1/2.2.9.Final or later for 2.2.x branches. For 2.0.x, upgrade to 2.0.36.SP1 or 2.0.39.Final. Ensure HTTP/2 functionality is tested after upgrade.

Recommended fix High confidence

Undertow 2.2.9.Final or 2.0.39.Final (or JBoss EAP 7.3.10+/7.4.1+ for JBoss deployments)

  1. Identify the Undertow version currently in use by examining pom.xml, build.gradle, or the application's dependency management
  2. For Maven projects, update the undertow version in pom.xml: Change <version>undertow-core</version> to a fixed version (e.g., 2.2.9.Final or 2.0.39.Final)
  3. For Gradle projects, update build.gradle: Change 'undertow-core:2.x.x' to 'undertow-core:2.2.9.Final' or 'undertow-core:2.0.39.Final'
  4. If using JBoss/Wildfly, update the server installation by upgrading to JBoss EAP 7.3.10+ or 7.4.1+ which includes fixed Undertow versions
  5. Run build and integration tests to verify the upgrade does not break existing functionality
  6. Redeploy the application with the updated dependencies
Caveat Minor: Undertow minor version upgrades typically maintain backward compatibility but always test in non-production first

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Fuse Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,080
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-3597 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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