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MEDIUM5.3

GHSA-5x3r-wrvg-rp6q

Netty HTTP/2: Advertised MAX_CONCURRENT_STREAMS are not enforced

Quick fix

GHSA-5x3r-wrvg-rp6q — io.netty:netty-codec-http2: upgrade to the fixed version with the command below.

# pom.xml: bump <version>4.2.15.Final</version> for io.netty:netty-codec-http2

Details

### Impact 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.

### Resources https://www.rfc-editor.org/rfc/rfc7540.html#section-6.5.2

Are you affected?

Enter the version of the package you're using.

Affected packages

Maven/io.netty:netty-codec-http2
Introduced in: 4.2.0.FinalFixed in: 4.2.15.Final
Fix# pom.xml: bump <version>4.2.15.Final</version> for io.netty:netty-codec-http2
Maven/io.netty:netty-codec-http2
Introduced in: 0Fixed in: 4.1.135.Final
Fix# pom.xml: bump <version>4.1.135.Final</version> for io.netty:netty-codec-http2

References