CVE-2026-73507 Netty: Denial of Service in XmlFrameDecoder via CPU Exhaustion
An unauthenticated remote attacker can cause denial of service in Netty by exhausting CPU resources through repeated XML closing tags.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-73507?
CVE-2026-73507 is a high-severity denial of service vulnerability in Netty Netty, published on 13 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-400
Which versions are affected by CVE-2026-73507?
4 open source packages ship an affected version, including io.netty:netty-codec-xml. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
io.netty:netty-codec-xml Maven | All versions | 4.1.136.Final |
io.netty:netty-codec-xml Maven | All versions | 4.1.136.Final |
io.netty:netty-codec-xml Maven | From 4.2.0.Final | 4.2.16.Final |
io.netty:netty-codec-xml Maven | From 4.2.0.Final | 4.2.16.Final |
Products include Netty Netty.
How do I fix CVE-2026-73507?
Upgrade io.netty:netty-codec-xml to a fixed version for your release line: 4.1.136.Final or 4.2.16.Final.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-73507 being exploited?
There is no known exploitation of CVE-2026-73507 in the wild and no public exploit code.
Other vulnerabilities in Netty Netty
- CVE-2026-75595 Netty: SNI Routing Bypass via Fragmented TLS ClientHello Causing Fallback to Default SslContext
- CVE-2026-75596 Netty: Fragmented ClientHello records trigger quadratic pre-handshake reassembly in default SNI parsing
- CVE-2026-59901 Netty Bzip2Decoder: Infinite Loop in RLE State Machine Leads to Event-Loop Thread Hang
- CVE-2026-55851 Netty codec-haproxy: Signed-Byte Sentinel Collision in HAProxyMessageDecoder Leads to Unbounded Memory Exhaustion
- CVE-2026-56745 Netty SpdyHttpDecoder: ByteBuf Reference Leak on RST_STREAM Leads to Native Memory Exhaustion
Sources
Also known as CLEANSTART-2026-RE51487, DEBIAN-CVE-2026-73507, GHSA-v74w-7mr3-4qg3, MINI-3684-rrvq-7wmf, MINI-4cpx-2wm8-39w5, MINI-9rr6-59wm-r756 and 8 more.