CVE catalog
CVE-2026-75596
Netty is an asynchronous, event-driven network application framework. Prior to 4.1.137.Final and 4.2.17.Final, the default io.netty.handler.ssl.SniHandler constructors use the pre-handshake ClientHell
- Severity
- High · CVSS 8.7
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - Published
- Updated
- Source
- [NVD] · [CVE record]
- EPSS
- 0.37% · Oct 25, 2026
Netty is an asynchronous, event-driven network application framework. Prior to 4.1.137.Final and 4.2.17.Final, the default io.netty.handler.ssl.SniHandler constructors use the pre-handshake ClientHello aggregation path in handler/src/main/java/io/netty/handler/ssl/SslClientHelloHandler.java at io.netty.handler.ssl.SslClientHelloHandler#decode, where handshakeBuffer.clear() and writeBytes() recopy all previously received body bytes for every additional TLS record. An unauthenticated remote peer can advertise a large ClientHello and deliver its body in thousands of tiny records, causing quadratic CPU work on the event loop before the TLS handshake completes and degrading TLS handling for other clients. This issue is fixed in versions 4.1.137.Final and 4.2.17.Final.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | netty | sid | 1:4.1.48-16 | vulnerable |
| Debian | netty | forky | 1:4.1.48-16 | vulnerable |
| Debian | netty | trixie | 1:4.1.48-10+deb13u1 | vulnerable |
| Debian | netty | trixie-security | 1:4.1.48-10+deb13u1 | vulnerable |
| Debian | netty | bookworm | 1:4.1.48-7+deb12u2 | vulnerable |
| Debian | netty | bookworm-security | 1:4.1.48-7+deb12u2 | vulnerable |
| Maven | io.netty:netty-handler | Not reported | 4.1.137.Final | fixed |
| Cpe | netty | Not reported | 4.2.17 | fixed |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | netty | source | sid | (unfixed) | not yet assigned | Not reported | [1145017] |
| Debian | netty | source | forky | (unfixed) | not yet assigned | Not reported | [1145017] |
| Debian | netty | source | trixie | (unfixed) | not yet assigned | Not reported | [1145017] |
| Debian | netty | source | bookworm | (unfixed) | not yet assigned | Not reported | [1145017] |
| Maven | io.netty:netty-handler | maven | Not reported | 4.1.137.Final | Not reported | GHSA-FCCG-MWVH-QQG4 | Not reported |
| Cpe | netty | cpe | Not reported | 4.2.17 | Not reported | NVD-CVE-2026-75596 | Not reported |
OpenFactory catalog packages
[Debian 12 (Bookworm)]
- [libnetty-java]Affected
Source package: [netty]
Details (4)
1:4.1.48-7+deb12u2· all · bookwormAffected
nvd · netty · debian · bookworm; nvd · netty · debian · 12
1:4.1.48-7+deb12u2· all · bookwormAffected
nvd · netty · debian · bookworm; nvd · netty · debian · 12
1:4.1.48-7+deb12u2· all · bookworm-securityAffected
nvd · netty · debian · bookworm; nvd · netty · debian · 12
1:4.1.48-7+deb12u2· all · bookworm-securityAffected
nvd · netty · debian · bookworm; nvd · netty · debian · 12
[Debian 13 (Trixie)]
- [libnetty-java]Affected
Source package: [netty]
Details (4)
1:4.1.48-10+deb13u1· all · trixieAffected
nvd · netty · debian · 13
1:4.1.48-10+deb13u1· all · trixieAffected
nvd · netty · debian · 13
1:4.1.48-10+deb13u1· all · trixie-securityAffected
nvd · netty · debian · 13
1:4.1.48-10+deb13u1· all · trixie-securityAffected
nvd · netty · debian · 13
Observed:
References
- [https://ftp.suse.com/pub/projects/security/csaf/opensuse-su-2026_11882-1.json]
- [https://github.com/advisories/GHSA-fccg-mwvh-qqg4]
- [https://github.com/netty/netty/commit/1b5abc6443b63726c72cdd285af2feb7ddbb8ff7]
- [https://github.com/netty/netty/commit/9e0519239108a69b7e9bbc5e9182ee139a0d7961]
- [https://github.com/netty/netty/pull/17213]
- [https://github.com/netty/netty/pull/17217]
- [https://github.com/netty/netty/releases/tag/netty-4.1.137.Final]
- [https://github.com/netty/netty/releases/tag/netty-4.2.17.Final]
- [https://github.com/netty/netty/security/advisories/GHSA-fccg-mwvh-qqg4]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-75596]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-75596]
- [https://security-tracker.debian.org/tracker/CVE-2026-75596]
- [https://wid.cert-bund.de/.well-known/csaf/white/2026/wid-sec-w-2026-2712.json]
[CERT-Bund public advisories] · [Debian Security Tracker] · [FIRST EPSS] · [GitHub Advisory Database] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [SUSE security advisories and VEX]