Vulnerability · Published Jun 12, 2026 · Assigned by GitHub_M
CVE-2026-44894Netty's Default QUIC token handler accepts any client-supplied token
High 7.5
In plain English
A high-severity security flaw in netty from netty. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 4% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Netty is a network application framework for development of protocol servers and clients. NoQuicTokenHandler is the tokenHandler used when the application does not set one. Prior to version 4.2.15.Final, its writeToken() returns false (server will not send Retry — acceptable), but validateToken() unconditionally `return 0`. In QuicheQuicServerCodec.handlePacket(), a non-negative return from validateToken() is interpreted as 'token is valid, ODCID starts at offset 0', causing the server to call quiche_accept as if the client's address had been validated by a Retry round-trip. Per RFC 9000 §8.1, a validated address lifts the 3× anti-amplification send limit. Thus any attacker who includes ANY non-empty token bytes in an Initial packet — with a spoofed victim source IP — causes the Netty server to treat the victim as validated and reflect full-size handshake flights (certificates, etc.) toward it without the 3× cap. The correct 'no token handler' semantics would be to return -1 (invalid) so the normal un-validated path and amplification limit apply. Version 4.2.15.Final patches the issue.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | netty | no fix listed | DEBIAN-CVE-2026-44894 |
| Debian:13 | netty | no fix listed | DEBIAN-CVE-2026-44894 |
| Debian:14 | netty | no fix listed | DEBIAN-CVE-2026-44894 |
| Maven | io.netty:netty-codec-classes-quic | 4.2.15.Final | GHSA-cmm3-54f8-px4j |
| Ubuntu:25.10 | netty | no fix listed | UBUNTU-CVE-2026-44894 |
| Ubuntu:26.10 | netty | no fix listed | UBUNTU-CVE-2026-44894 |
Affected products (as reported)
Weakness: CWE-940, CWE-346 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
References
- https://github.com/netty/netty/security/advisories/GHSA-cmm3-54f8-px4j x_refsource_CONFIRM
- https://github.com/netty/netty/releases/tag/netty-4.2.15.Final x_refsource_MISC
- https://access.redhat.com/security/cve/CVE-2026-44894 vdb-entry, x_refsource_REDHAT
- RHBZ#2488380 issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44894.json x_sadp-csaf-vex