CVE-2026-44894
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 · uneditedNetty is a network application framework for development of protocol servers and clients. NoQuicTokenHandler is the tokenHandler used when the application does not set one. Prior to version 4.2.15.Final, its writeToken() returns false (server will not send Retry — acceptable), but validateToken() unconditionally `return 0`. In QuicheQuicServerCodec.handlePacket(), a non-negative return from validateToken() is interpreted as 'token is valid, ODCID starts at offset 0', causing the server to call quiche_accept as if the client's address had been validated by a Retry round-trip. Per RFC 9000 §8.1, a validated address lifts the 3× anti-amplification send limit. Thus any attacker who includes ANY non-empty token bytes in an Initial packet — with a spoofed victim source IP — causes the Netty server to treat the victim as validated and reflect full-size handshake flights (certificates, etc.) toward it without the 3× cap. The correct 'no token handler' semantics would be to return -1 (invalid) so the normal un-validated path and amplification limit apply. Version 4.2.15.Final patches 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 confidenceIn Netty's QUIC implementation prior to version 4.2.15.Final, the NoQuicTokenHandler.validateToken() incorrectly returns 0 instead of -1 for invalid tokens. This causes QuicheQuicServerCodec to misinterpret missing/invalid tokens as address-validated, bypassing the RFC 9000 §8.1 3x anti-amplification limit. Attackers can spoof victim IP addresses and send Initial packets with any non-empty token to trigger reflection of full-size handshake responses toward victims.
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>= 4.2.0, < 4.2.15CVSS 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
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
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 checksWork through these to decide whether this CVE applies to you.
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Identify Netty QUIC usageInspect your project's dependencies (Maven pom.xml, Gradle build.gradle, or JAR manifests) for the netty-codec-quic or com.typesafe.netty:netty-codec-quic artifacts. Also check for any QUIC-related configuration files or code imports from io.netty.incubator.codec.quic.Affected if Netty QUIC module is present in the runtime dependencies or classpath
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Determine installed Netty versionLocate the netty-common or netty-codec-quic JAR file in your deployment and read its filename for the version (e.g., netty-codec-quic-4.2.14.Final.jar). Alternatively, query the NettyVersion class or check your dependency management system for the resolved version.Affected if The Netty version resolves to 4.2.0 through 4.2.14 inclusive (anything below 4.2.15.Final)
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Verify QUIC server is configuredSearch configuration files (application.conf, application.yml, or custom QUIC config classes) for QuicServerBootstrap, QuicClientBootstrap, or the codec setup using QuicCodecBuilder. Check if the application binds to a UDP port for QUIC traffic.Affected if A QUIC server or client endpoint is actively configured and bound to a UDP port
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Confirm token validation is in useReview the NoQuicTokenHandler class in your Netty JAR or source. In the validateToken() method, verify whether it returns -1 for invalid/empty tokens. If the method body simply returns 0 unconditionally, the vulnerability is present.Affected if validateToken() returns 0 for any non-null token instead of validating and returning -1 for invalid tokens
If Netty QUIC module version is 4.2.0 through 4.2.14 and a QUIC endpoint is actively running, the anti-amplification check is bypassed and the environment is affected.
Generated from the published advisory. Verify against your own configuration.
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 · scoped4.2.15
Upgrade to Netty version 4.2.15.Final or later, which patches NoQuicTokenHandler.validateToken() to return -1 (invalid) instead of 0, restoring proper anti-amplification limits.
4.2.15.Final
- Identify all Netty deployments using versions 4.2.0 through 4.2.14 that use the QUIC server components
- Upgrade Netty to version 4.2.15.Final or later in all affected environments
- Verify the upgrade by confirming the NoQuicTokenHandler.validateToken() method now correctly returns -1 for invalid tokens rather than 0
- Test QUIC server functionality after upgrade to ensure normal handshake and anti-amplification limits work correctly
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-44894 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-44894 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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