Netty: [HttpContentEncoder] Unbounded Per-Connection Queue Growth via HTTP/1.1 Pipelining Leads to Denial of Service (CVE-2026-59899) | HOL Guard CVE

High · CVSS 7.5CVE-2026-59899GHSA-Q4F6-JM68-57WW

Netty: [HttpContentEncoder] Unbounded Per-Connection Queue Growth via HTTP/1.1 Pipelining Leads to Denial of Service

Answer in brief

CVE-2026-59899 records a High severity (CVSS 7.5) vulnerability in Netty: [HttpContentEncoder] Unbounded Per-Connection Queue Growth via HTTP/1.1 Pipelining Leads to Denial of Service. The current sources do not mark it as known exploited. The current feed maps io.netty:netty-codec-http (maven), io.netty:netty-codec-http (maven). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jul 22, 2026Updated Sep 10, 2026Source checked Sep 10, 2026First seen by HOL Aug 6, 2026Material review Sep 10, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.5
Exploitation: Not marked as known exploited
Affected software: 3 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps io.netty:netty-codec-http (maven), io.netty:netty-codec-http (maven). Check affected ranges and fixed versions before updating.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:a:netty:netty::::::::	Not reported	Not reported

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
io.netty:netty-codec-httpmaven	>=4.2.0.Final <4.2.16.Final	4.2.16.Final
io.netty:netty-codec-httpmaven	>=0 <4.1.136.Final	4.1.136.Final

Recommended response

Check inventory. Check lockfiles and deployed manifests for io.netty:netty-codec-http, io.netty:netty-codec-http.
Review the reported fix. Update io.netty:netty-codec-http to 4.2.16.Final; io.netty:netty-codec-http to 4.1.136.Final if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jul 22, 2026
Evidence: source:nvd:source_dates:source-dates:record
Source modified
Sep 10, 2026
Evidence: source:nvd:source_dates:source-dates:record
First seen by HOL
Aug 6, 2026

Sources and claim methodology

Upstream source description

Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, `HttpContentEncoder` (the superclass of the production handler `HttpContentCompressor`) maintains a per-channel `ArrayDeque<CharSequence>` named `acceptEncodingQueue` that accumulates attacker-controlled data without any size limit. The queue is filled on the I/O thread for every inbound HTTP request and drained only when the application later writes a non-1xx response. This creates a resource exhaustion vulnerability when an attacker exploits HTTP/1.1 pipelining to flood the connection with requests faster than the application produces responses. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.

Quoted source text, attributed separately from HOL analysis.