Netty susceptible to HTTP/2 Reset Attack with different on-the-wire signature
Summary
Netty HTTP/2 max header size handling produces attack similar to HTTP/2 Rapid Reset.
Details
There is a setting in the http2 specification called SETTINGS_MAX_HEADER_LIST_SIZE. According to the RFC: “This advisory setting informs a peer of the maximum field section size that the sender is prepared to accept, in units of octets.”
When a client sends that setting to Netty, it appears that Netty will behave as follows:
- Read the request
- Proxy the request to the origin
- Attempt to produce a response
- Create an exception while writing the headers for the response
Functionally, this should be similar to the http2 reset attack, but with a different on-the-wire signature.
Remediation
When speaking with clients, Netty should potentially treat this as “advisory” and ignore it. It would be best to ignore the SETTINGS_MAX_HEADER_LIST_SIZE setting from clients (or ignore it when sending to clients). According to the spec, a server does not need to honor this advisory setting, and it appears that other http/2 implementations ignore it when acting as a server.
Impact
This is a DDoS attack similar to the HTTP/2 Rapid Reset Attack.
Credit
Jonathan Looney (Engineering, Netflix)
Contact
Ashley Tolbert (Security, Netflix) - artolbert@netflix.com
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Java / Kotlin (Maven) | io.netty:netty-codec-http2 | >= 4.2.0.Final, < 4.2.15.Final, < 4.1.135.Final | 4.2.15.Final, 4.1.135.Final |
References
- https://github.com/netty/netty/security/advisories/GHSA-563q-j3cm-6jxm
- https://nvd.nist.gov/vuln/detail/CVE-2026-50560
- https://github.com/netty/netty
- https://github.com/netty/netty/releases/tag/netty-4.1.135.Final
- https://github.com/netty/netty/releases/tag/netty-4.2.15.Final
- https://www.rfc-editor.org/rfc/rfc9113.html#name-defined-settings
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L- Weakness (CWE)
CWE-770- Platform
- Java / Kotlin (Maven)
- Package
io.netty:netty-codec-http2- Disclosed
- 15.06.2026
- Updated
- 11.10.2026 13:20
Sources and licenses
OSV / GitHub Advisory Database - GHSA-563q-j3cm-6jxm - CC BY 4.0
Vulnerability history: io.netty:netty-codec-http2
All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 11
- First → latest
- 03.2021 07.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 5
- Medium 6
Disclosures per year
- 2021: 2
- 2022: 0
- 2023: 1
- 2024: 0
- 2025: 1
- 2026: 7
-
Netty susceptible to HTTP/2 Reset Attack with different on-the-wire signature this entry
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