Netty has a Vulnerable Default Configuration Which Leads to Denial of Service via Unbounded HTTP/3 Header Size

published 2026-06-08 5 mo ago modified 2026-09-10 1 mo ago also EUVD-2026-36386 , GHSA-c2rx-5r8w-8xr2

cvss: 7.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 20%
public exploits: 0; none known

Netty is a network application framework for development of protocol servers and clients. Prior to version 4.2.15.Final, the default configuration of the `Http3ConnectionHandler` in the Netty HTTP/3 codec lacks an enforced maximum header size limit. When a peer does not explicitly specify `HTTP3_SETTINGS_MAX_FIELD_SECTION_SIZE`, the implementation defaults to an unbounded limit. This insecure default configuration allows a malicious client or server to send an enormous number of headers, leading to a memory exhaustion Denial of Service via an `OutOfMemoryError`. Version 4.2.15.Final contains a patch.

Patch / fix

fixed in 3 links 1

maven io.netty:netty-codec-http3 4.2.15.Final
io.netty netty-codec-http3 4.2.15.Final
netty netty 4.2.15.Final

github.com/netty/netty/releases/tag/netty-4.2.15.Final release

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: partial
Assessed: 4 mo ago (2026-06-12)

Exploit prediction

0.28% chance of exploitation in the next 30 days, higher than 20% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem	package	affected	fixed in
maven	io.netty:netty-codec-http3	>=4.2.0.Final, <4.2.15.Final	4.2.15.Final

Affected products

netty netty

Classification

Weakness

CWE-400 Uncontrolled Resource Consumption
CWE-1188 Initialization of a Resource with an Insecure Default

References

github.com /netty/netty/security/advisories/GHSA-c2rx-5r8w-8xr2
web, vendor-advisory
github.com /netty/netty/releases/tag/netty-4.2.15.Final
web, release-notes
nvd.nist.gov /vuln/detail/CVE-2026-44892
advisory
github.com /netty/netty
package

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary