CVE-2026-55833 Details
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.
A vulnerability exists in the Netty framework in versions prior to 4.1.136.Final and 4.2.16.Final. The issue arises in the SPDY protocol handling, where the zlib-compressed header blocks are improperly processed. The decoder continues to inflate these blocks even after surpassing the maximum header size, which has been marked as truncated. This flaw allows a remote peer to send a small compressed 'HEADERS' block that expands into significantly larger raw header data, effectively bypassing the size limitations. The consequence is a denial-of-service condition, characterized by increased CPU usage and memory allocation, caused by the compression of data being handled in the SpdyFrameCodec pipeline.
Users can upgrade to Netty versions 4.1.136.Final or 4.2.16.Final to address this vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jul 21, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-400 | Uncontrolled Resource Consumption | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| netty netty | >= 4.1.0, < 4.1.136 >= 4.2.0, < 4.2.16 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 23, 2026 | Reanalysis | [email protected] |
| Jul 22, 2026 | Initial Analysis | [email protected] |
| Jul 21, 2026 | CVE Modified | CISA-ADP |
| Jul 21, 2026 | New CVE Received | [email protected] |