How severe is CVE-2026-50560?

No CVSS score has been assigned to CVE-2026-50560 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-50560?

CVE-2026-50560 affects the following packages: io.netty:netty-codec-http2 (Maven), io.netty:netty-codec-http2 (Maven). Ecosystems affected: Maven.

How do I fix CVE-2026-50560?

Update io.netty:netty-codec-http2 to 4.2.15.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-50560 is resolved across your whole dependency graph.

How do I detect CVE-2026-50560 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.netty:netty-codec-http2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-50560 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2026-50560 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-50560 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-50560?

CVE-2026-50560 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 34th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-50560?

CVE-2026-50560 is classified as CWE-770 (CWE-770). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-50560 published, and has it been updated?

CVE-2026-50560 was published on June 12, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

Not in CISA KEV

CVE-2026-50560 — netty-codec-http2

CVE-2026-50560 is a CWE-770 vulnerability in io.netty:netty-codec-http2. A fix is available for io.netty:netty-codec-http2 — see the affected versions and patch details below.

Netty susceptible to HTTP/2 Reset Attack with different on-the-wire signature

Also known asGHSA-563q-j3cm-6jxm

Published

Jun 12, 2026

Updated

Oct 21, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 25, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-50560.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk-0.13%

Lower risk than most CVEs34th percentile — riskier than 34% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

2 pkgs affected

☕io.netty:netty-codec-http2☕io.netty:netty-codec-http2

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

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) - [email protected]

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`io.netty:netty-codec-http2`	≥ 4.2.0.Final&&< 4.2.15.Final	4.2.15.Final`io.netty:netty-codec-http2:4.2.15.Final`
☕Maven	`io.netty:netty-codec-http2`	all versions	4.1.135.Final`io.netty:netty-codec-http2:4.1.135.Final`

Affected Products

1 product · 2 configurations

Application

nettynetty

≥ 4.2.0 && < 4.2.15

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.netty:netty-codec-http2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update io.netty:netty-codec-http2 to 4.2.15.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-50560 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

This flaw in Netty's HTTP/2 protocol handling is rated Moderate. A remote, unauthenticated attacker can trigger a denial of service by sending a crafted `SETTINGS_MAX_HEADER_LIST_SIZE` frame, causing an exception during response header processing. This can disrupt services utilizing Netty for HTTP/2 communication.

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

Source: Red Hat security advisory for CVE-2026-50560 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat build of Quarkus 3.27.4.SP1	`io.netty/netty-codec-http2:4.1.135.Final-redhat-00001`	RHSA-2026:26018
Red Hat build of Quarkus 3.33.2.SP1	`io.netty/netty-codec-http2:4.1.135.Final-redhat-00001`	RHSA-2026:26017

Frequently Asked Questions

### 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](https://www.rfc-editor.org/rfc/rfc9113.html#name-defined-settings): “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 - C

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