CVE-2026-73507
Received Received - Intake

Denial of Service in Netty via XML Frame Decoder

Publication date: 2026-08-13

Last updated on: 2026-08-13

Assigner: GitHub, Inc.

Description
Netty is an asynchronous, event-driven network application framework. Prior to 4.1.136.Final and 4.2.16.Final, io.netty.handler.codec.xml.XmlFrameDecoder.decode() failed to preserve closing-tag parser state across invocations, so an unauthenticated remote attacker could trickle-feed repeated </ sequences that repeatedly rescanned the accumulated buffer and exhausted an EventLoop thread's CPU, causing denial of service with a maxFrameLength of 1 MB. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.

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Meta Information

Published
2026-08-13
Last Modified
2026-08-13
Generated
2026-08-13
AI Q&A
2026-08-13
EPSS Evaluated
N/A
NVD
CVE-2026-73507
EUVD
EUVD-2026-58083

Affected Vendors & Products

Showing 4 associated CPEs
Vendor Product Version / Range
netty netty From 4.1.136.Final (inc)
netty netty From 4.2.16.Final (inc)
netty netty to 4.1.136.Final (exc)
netty netty to 4.2.16.Final (exc)

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-400 The product does not properly control the allocation and maintenance of a limited resource.

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Executive Summary

CVE-2026-73507 is a Denial of Service (DoS) vulnerability in Netty's XmlFrameDecoder component. It affects versions up to 4.2.15.Final and 4.1.135.Final. The issue occurs when an attacker sends malicious XML payloads with repeated '</' sequences. This causes the decoder to repeatedly scan buffers for closing '>' characters, exhausting CPU resources on the server's EventLoop thread and making it unresponsive.

Detection Guidance

Monitor for high CPU usage on EventLoop threads in Netty servers using XmlFrameDecoder. Check for repeated '</' sequences in incoming XML payloads via network traffic inspection tools like Wireshark or tcpdump. Enable application logging to detect excessive buffer scanning events.

Impact Analysis

This vulnerability can cause your Netty-based server to become unresponsive or crash due to high CPU usage. It requires no authentication or user interaction, meaning attackers can exploit it remotely. The impact includes degraded service quality, potential downtime, and increased operational costs for recovery.

Mitigation Strategies

Upgrade Netty to versions 4.1.136.Final or 4.2.16.Final or later. Disable XmlFrameDecoder if not required. Implement rate limiting for XML parsing requests. Use network-level protections to block malformed XML payloads.

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