# CVE-2026-55833: Netty SPDY zlib header block continues decoded expansion after maxHeaderSize truncation

> CVE-2026-55833: Netty SPDY zlib header block continues decoded expansion after maxHeaderSize truncation. CVSS 7.5 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-55833
Last updated: 2026-07-23T13:34:45Z

- Published: 2026-07-20 23:18 UTC · Updated: 2026-07-23 13:34 UTC · Assigner: GitHub\_M
- CVSS: 7.5 (CVSS 3.1) · Severity: High · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS: 0.66%, 52th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-400

## Description

Netty is a network application framework for development of protocol servers and clients. Prior to 4.1.136.Final and 4.2.16.Final, Netty SPDY header decoding continues inflating zlib-compressed header blocks after the raw header parser has exceeded \`maxHeaderSize\` and marked the frame truncated in \`SpdyFrameCodec\`, allowing a remote peer to send a small compressed \`HEADERS\` block that expands into much larger raw header data and causes compression-amplified CPU and allocation churn. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.

## Affected vendors and products

- netty: netty

## Tracked companies

- [Bitbucket](https://rewindex.com/company/bitbucket.md)
- [Confluence](https://rewindex.com/company/confluence.md)
- [Jira](https://rewindex.com/company/jira.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-55833)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-55833)
- [https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b](https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b)
- [https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6](https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6)
- [https://github.com/netty/netty/releases/tag/netty-4.1.136.Final](https://github.com/netty/netty/releases/tag/netty-4.1.136.Final)
- [https://github.com/netty/netty/releases/tag/netty-4.2.16.Final](https://github.com/netty/netty/releases/tag/netty-4.2.16.Final)
- [https://github.com/netty/netty/security/advisories/GHSA-mvh2-crg5-v77c](https://github.com/netty/netty/security/advisories/GHSA-mvh2-crg5-v77c)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-55833 · Markdown: https://rewindex.com/cve/CVE-2026-55833.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-55833 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:13:40.800Z