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Netty netty-codec-http CVE-2026-59899

| EUVDEUVD-2026-50443 MEDIUM
Allocation of Resources Without Limits or Throttling (CWE-770)
2026-07-22 https://github.com/netty/netty GHSA-q4f6-jm68-57ww
Denial Of Service
6.9
CVSS 4.0 · Vendor: https://github.com/netty/netty
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Severity by source

Vendor (https://github.com/netty/netty) PRIMARY
6.9 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vuln.today AI
7.5 HIGH

Network-reachable via standard HTTP/1.1 pipelining with no authentication or interaction required; impact is availability-only heap exhaustion.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE
5.3 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Red Hat
7.5 HIGH
qualitative

Primary rating from Vendor (https://github.com/netty/netty).

CVSS VectorVendor: https://github.com/netty/netty

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

4
CVSS changed
Jul 29, 2026 - 18:22 NVD
6.9 (MEDIUM)
Source Code Evidence Fetched
Jul 22, 2026 - 22:23 vuln.today
Analysis Generated
Jul 22, 2026 - 22:23 vuln.today
CVE Published
Jul 22, 2026 - 21:49 cve.org
MEDIUM

Blast Radius

ecosystem impact
† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth
  • 344 maven packages depend on io.netty:netty-codec-http (32 direct, 312 indirect)

Ecosystem-wide dependent count for version 4.2.0.Final.

DescriptionCVE.org

Impact

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.

AnalysisAI

Resource exhaustion in Netty's HttpContentEncoder allows unauthenticated remote attackers to crash JVM-based servers via HTTP/1.1 pipelining. The per-channel acceptEncodingQueue accumulates attacker-controlled Accept-Encoding header values on the I/O thread without any bound, and is only drained when the application emits a non-1xx response - meaning a client pipelining requests faster than the server responds can inflate heap usage without limit. Vendor-released patches are available in 4.1.136.Final and 4.2.16.Final; no public exploit or CISA KEV listing is present at time of analysis.

Technical ContextAI

The vulnerability exists in the Maven artifact io.netty:netty-codec-http (CPE: pkg:maven/io.netty:netty-codec-http). HttpContentEncoder is the abstract superclass of the commonly-used HttpContentCompressor handler, which transparently compresses HTTP response bodies. To select the appropriate encoding for each response, the handler reads the Accept-Encoding header from each inbound request and enqueues it in a per-channel java.util.ArrayDeque<CharSequence> named acceptEncodingQueue on the I/O thread. HTTP/1.1 pipelining allows a client to send multiple requests over a single TCP connection without waiting for individual responses, meaning this queue can accumulate indefinitely if the application is slower to respond than the attacker is to send requests. CWE-770 (Allocation of Resources Without Limits or Throttling) precisely captures the root cause: no capacity cap, backpressure mechanism, or watermark exists on this queue, allowing heap exhaustion proportional to the attacker's ability to pipeline requests.

RemediationAI

Upgrade io.netty:netty-codec-http to 4.1.136.Final (4.1.x users) or 4.2.16.Final (4.2.x users) per the Netty release pages at https://github.com/netty/netty/releases/tag/netty-4.1.136.Final and https://github.com/netty/netty/releases/tag/netty-4.2.16.Final and the advisory at https://github.com/netty/netty/security/advisories/GHSA-q4f6-jm68-57ww. If an immediate upgrade is not feasible, removing HttpContentCompressor and HttpContentEncoder from the Netty channel pipeline eliminates the vulnerable code path at the cost of disabling server-side response compression (clients will receive uncompressed responses, increasing bandwidth). As a network-layer compensating control, placing an HTTP-aware reverse proxy such as nginx in front of the Netty service and configuring it to disable or limit HTTP/1.1 pipelining can reduce attack surface, though this adds operational overhead and does not address the root cause. JVM heap limits (-Xmx) do not prevent the attack but constrain the blast radius by causing an OutOfMemoryError rather than unbounded growth.

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Not-Affected
SUSE Linux Enterprise Desktop 15 SP7 Not-Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Not-Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Not-Affected
SUSE Linux Enterprise Module for Development Tools 15 SP7 Not-Affected

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CVE-2026-59899 vulnerability details – vuln.today
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