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NettyApplication

CVE-2026-47244

MEDIUM · 5.3 CVSS v3.1 Published 2026-06-12
Fix available
A fix is available. Upgrade to 4.1.135 / 4.2.15 or later.
See remediation →
62/100
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
Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, DefaultHttp2Connection.DefaultEndpoint initialises maxActiveStreams/maxStreams to Integer.MAX_VALUE, and Http2Settings never inserts SETTINGS_MAX_CONCURRENT_STREAMS by default (Http2Settings.java:305-307 only clamps a user-supplied value). Unless the application explicitly calls initialSettings().maxConcurrentStreams(n), a Netty HTTP/2 server advertises no limit and enforces none locally. Each open stream allocates a DefaultStream object, PropertyMap slots, flow-controller state and IntObjectHashMap entry; with ~2^30 permissible odd stream IDs a single TCP connection can create hundreds of thousands of long-lived stream objects. This is also the precondition for CVE-2023-44487-style Rapid-Reset amplification, where the absence of a low concurrent cap multiplies backend work. Versions 4.1.135.Final and 4.2.15.Final patch the issue.

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

Netty's HTTP/2 implementation fails to set a default limit on concurrent streams. The DefaultHttp2Connection.DefaultEndpoint initializes maxActiveStreams/maxStreams to Integer.MAX_VALUE, and Http2Settings doesn't insert SETTINGS_MAX_CONCURRENT_STREAMS by default. This allows an attacker to open hundreds of thousands of streams on a single TCP connection, causing resource exhaustion and enabling Rapid-Reset style amplification attacks (CVE-2023-44487).

MitigationUpgrade Netty to versions 4.1.135.Final or 4.2.15.Final, which contain the patch. Alternatively, explicitly call initialSettings().maxConcurrentStreams(n) to enforce a stream limit.

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
NettyApplication
Affected:< 4.1.135>= 4.2.0, < 4.2.15

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
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

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

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. Check Netty version
    Inspect the netty-common or netty-transport JAR file manifest, or review Maven/Gradle dependency declarations for the netty version
    Affected if Version is below 4.1.135, or 4.2.0 and above but below 4.2.15
  2. Confirm HTTP/2 is enabled
    Search the codebase for Http2FrameCodec, Http2MultiplexHandler, or HTTP/2 server/bootstrap configuration patterns
    Affected if HTTP/2 is actively configured and in use
  3. Verify explicit stream limit configuration
    Search for calls to initialSettings().maxConcurrentStreams(n) or equivalent configuration that sets SETTINGS_MAX_CONCURRENT_STREAMS
    Affected if No explicit maxConcurrentStreams limit is configured, allowing the default unbounded value (Integer.MAX_VALUE) to be used
  4. Inspect Http2Settings initialization
    Examine how Http2Settings is constructed in the application; verify SETTINGS_MAX_CONCURRENT_STREAMS is present in the settings object
    Affected if Http2Settings uses defaults without SETTINGS_MAX_CONCURRENT_STREAMS explicitly set

You are affected if your Netty version falls in the vulnerable range AND HTTP/2 is enabled without an explicit maxConcurrentStreams limit configured.

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 4.1.135 / 4.2.15 or later
Fixed in 4.1.1354.2.15
Interim mitigation

Upgrade Netty to versions 4.1.135.Final or 4.2.15.Final, which contain the patch. Alternatively, explicitly call initialSettings().maxConcurrentStreams(n) to enforce a stream limit.

Recommended fix High confidence

4.1.135.Final (for 4.1.x line) or 4.2.15.Final (for 4.2.x line)

  1. Identify your current Netty version by checking your Maven pom.xml or Gradle build.gradle dependencies
  2. For Netty 4.1.x users: Update the Netty dependency version to 4.1.135.Final
  3. For Netty 4.2.x users: Update the Netty dependency version to 4.2.15.Final
  4. If using Maven, update the version in pom.xml: change netty version to 4.1.135.Final or 4.2.15.Final
  5. If using Gradle, update the version in build.gradle: change io.netty:netty-all to 4.1.135.Final or 4.2.15.Final
  6. Rebuild and test the application to ensure compatibility
  7. Deploy the updated application

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

Fix this in Netty Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
20.0 hours of engineering $3,440
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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-2026-47244 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data