High severity · published Jul 21, 2026
CVE-2026-56816
Netty: Memory Exhaustion via HTTP/3 Reserved Frame Types
7.5
CVSS
0.6%
EPSS
No
On KEV
Description
Netty is a network application framework for development of protocol servers and clients. Prior to 4.2.16.Final, Netty's `Http3FrameCodec` buffers incoming data for HTTP/3 reserved frame types up to the wire-specified payload length without limits; `decodeFrame` trusts `payLoadLength`, allowing an attacker to open multiple QUIC streams and send reserved frames with very large payload lengths to cause memory exhaustion and denial of service. This issue is fixed in version 4.2.16.Final.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 51% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NE
netty · netty
< 4.2.16.Final · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-56816
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-56816
Patch
https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b
Release Notes
https://github.com/netty/netty/releases/tag/netty-4.2.16.Final
Exploit
https://github.com/netty/netty/security/advisories/GHSA-hpcc-26xq-25fv
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