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… (CVE-2026-55833)
Description
A vulnerability in Netty's SPDY codec HTTP component prior to versions 4.1.136.Final and 4.2.16.Final allows continued inflation of zlib-compressed header blocks after the raw header parser exceeds the maxHeaderSize limit. This can cause a small compressed header block to expand into a much larger raw header, resulting in denial of service due to excessive CPU and memory usage. The issue affects pipelines using SpdyFrameCodec without upstream compressed-frame-size or connection-rate limits. Exploitation requires a remote unauthenticated attacker able to send SPDY frames to the vulnerable Netty pipeline.
CVSS v3.1
Score 7.5high
Affected software
pkg:deb/ubuntu/netty?arch=source&distro=esm-infra-legacy/trustypkg:deb/ubuntu/netty?arch=source&distro=esm-apps-legacy/xenialpkg:deb/ubuntu/netty?arch=source&distro=esm-apps/bionicpkg:deb/ubuntu/netty?arch=source&distro=esm-apps/focalpkg:deb/ubuntu/netty?arch=source&distro=esm-apps/jammypkg:deb/ubuntu/netty?arch=source&distro=esm-apps/noblepkg:deb/ubuntu/netty?arch=source&distro=stonkingpkg:deb/ubuntu/netty?arch=source&distro=esm-apps/resoluteRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-55833 describes a denial of service vulnerability in Netty's SPDY codec HTTP component where zlib-compressed header blocks continue inflating after the raw header parser has marked the frame as truncated due to exceeding maxHeaderSize. This leads to disproportionate resource consumption (CPU and memory). The vulnerability affects Netty versions prior to 4.1.136.Final and 4.2.16.Final, specifically pipelines using SpdyFrameCodec without limits on compressed frame size or connection rate. An unauthenticated remote attacker can exploit this by sending crafted SPDY frames to trigger excessive resource usage.
Potential Impact
Successful exploitation results in denial of service through excessive CPU and memory consumption on the affected system. There is no impact on confidentiality or integrity. The attack requires the ability to send SPDY frames to the vulnerable Netty pipeline remotely without authentication.
Mitigation Recommendations
A fix is available in Netty versions 4.1.136.Final and 4.2.16.Final and later. Users should upgrade to these or newer versions to remediate the vulnerability. Additionally, implementing upstream limits on compressed-frame size or connection rate can mitigate the risk. No vendor advisory content was provided to indicate otherwise.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-mvh2-crg5-v77c
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-55833"]
- Ecosystems
- ["Maven"]
- Database Specific Severity
- HIGH
- Cvss Version
- 3.1
Threat ID: 6a6150e99c2644c7f8da2342
Added to database: 07/22/2026, 23:23:21 UTC
Last enriched: 10/18/2026, 04:49:38 UTC
Last updated: 10/21/2026, 13:20:22 UTC
Views: 111
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