Netty has a Vulnerable Default Configuration Which Leads to Denial of Service via Unbounded HTTP/3 Header Size

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-44892: 0.28% estimated exploitation activity in the next 30 days; percentile 20.41 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The default configuration of the Http3ConnectionHandler in the Netty HTTP/3 codec lacks an enforced maximum header size limit. When a peer does not explicitly specify HTTP3SETTINGSMAXFIELDSECTIONSIZE, the implementation defaults to an unbounded limit. This insecure default configuration allows a malicious client or server to send an enormous number of headers, leading to a memory exhaustion Denial of Service via an OutOfMemoryError. Details Netty securely limits header sizes for older protocols. In HTTP/1.1, Netty strictly enforces an 8192-byte limit out-of-the-box via HttpObjectDecoder. For HTTP/2, while RFC 9113 specifies that SETTINGSMAXHEADERLISTSIZE defaults to unlimited, Netty securely overrides this RFC default by enforcing an 8192-byte limit (Http2CodecUtil.DEFAULTHEADERLISTSIZE). However, this secure-by-default configuration is missing in the HTTP/3 implementation. While Netty provides a mechanism to configure the maximum header field section size via Http3Settings,…

Published by the source

8 Jun 2026, 19:02 UTC

Last modified by the source

12 Jun 2026, 19:27 UTC

Source last checked

26 Oct 2026, 16:46 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-c2rx-5r8w-8xr2

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# Patch Next advisory brief: CVE-2026-44892

Advisory: Netty has a Vulnerable Default Configuration Which Leads to Denial of Service via Unbounded HTTP/3 Header Size
IDs: CVE-2026-44892, GHSA-c2rx-5r8w-8xr2
Record: https://patchnext.com/advisories/cve-2026-44892 (revision 1, source checked 26 Oct 2026, 16:46 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: io.netty:netty-codec-http3 4.2.15.Final. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven io.netty:netty-codec-http3: affected >= 4.2.0.Final, <= 4.2.14.Final; fixed in 4.2.15.Final

## Suggested inspection (read-only)
- Maven io.netty:netty-codec-http3: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on io.netty:netty-codec-http3.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-c2rx-5r8w-8xr2 (GitHub-reviewed advisory GHSA-c2rx-5r8w-8xr2 lists affected ranges: Maven io.netty:netty-codec-http3 >=4.2.0.Final <=4.2.14.Final)

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