ubuntu-cve-2026-75596
Vulnerability from osv_ubuntu
Published
2026-08-21 00:00
Modified
2026-08-21 00:00
Summary
Details
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.
Severity
N/A (UNKNOWN)
References
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libnetty-java",
"binary_version": "1:3.2.6.Final-2+deb8u2ubuntu0.1~esm1"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:14.04:LTS",
"name": "netty",
"purl": "pkg:deb/ubuntu/netty@1:3.2.6.Final-2+deb8u2ubuntu0.1~esm1?arch=source\u0026distro=esm-infra-legacy/trusty"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:3.2.6.Final-2",
"1:3.2.6.Final-2+deb8u2build0.14.04.1~esm1",
"1:3.2.6.Final-2+deb8u2ubuntu0.1~esm1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libnetty-java",
"binary_version": "1:4.0.34-1ubuntu0.1~esm5"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:16.04:LTS",
"name": "netty",
"purl": "pkg:deb/ubuntu/netty@1:4.0.34-1ubuntu0.1~esm5?arch=source\u0026distro=esm-apps-legacy/xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:3.2.6.Final-2",
"1:4.0.32-1",
"1:4.0.33-1",
"1:4.0.34-1",
"1:4.0.34-1ubuntu0.1~esm1",
"1:4.0.34-1ubuntu0.1~esm2",
"1:4.0.34-1ubuntu0.1~esm3",
"1:4.0.34-1ubuntu0.1~esm4",
"1:4.0.34-1ubuntu0.1~esm5"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libnetty-java",
"binary_version": "1:4.1.7-4ubuntu0.1+esm7"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:18.04:LTS",
"name": "netty",
"purl": "pkg:deb/ubuntu/netty@1:4.1.7-4ubuntu0.1+esm7?arch=source\u0026distro=esm-apps/bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:4.1.7-4",
"1:4.1.7-4ubuntu0.1~esm1",
"1:4.1.7-4ubuntu0.1",
"1:4.1.7-4ubuntu0.1+esm1",
"1:4.1.7-4ubuntu0.1+esm2",
"1:4.1.7-4ubuntu0.1+esm3",
"1:4.1.7-4ubuntu0.1+esm4",
"1:4.1.7-4ubuntu0.1+esm5",
"1:4.1.7-4ubuntu0.1+esm6",
"1:4.1.7-4ubuntu0.1+esm7"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libnetty-java",
"binary_version": "1:4.1.45-1ubuntu0.1~esm7"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:20.04:LTS",
"name": "netty",
"purl": "pkg:deb/ubuntu/netty@1:4.1.45-1ubuntu0.1~esm7?arch=source\u0026distro=esm-apps/focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:4.1.33-1",
"1:4.1.33-2",
"1:4.1.33-3",
"1:4.1.45-1",
"1:4.1.45-1ubuntu0.1~esm1",
"1:4.1.45-1ubuntu0.1~esm2",
"1:4.1.45-1ubuntu0.1~esm3",
"1:4.1.45-1ubuntu0.1~esm4",
"1:4.1.45-1ubuntu0.1~esm6",
"1:4.1.45-1ubuntu0.1~esm7"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libnetty-java",
"binary_version": "1:4.1.48-4+deb11u2ubuntu0.2+esm1"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:22.04:LTS",
"name": "netty",
"purl": "pkg:deb/ubuntu/netty@1:4.1.48-4+deb11u2ubuntu0.2+esm1?arch=source\u0026distro=esm-apps/jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:4.1.48-4",
"1:4.1.48-4+deb11u1build0.22.04.1",
"1:4.1.48-4+deb11u2build0.22.04.1",
"1:4.1.48-4+deb11u2ubuntu0.1~esm1",
"1:4.1.48-4+deb11u2ubuntu0.1~esm2",
"1:4.1.48-4+deb11u2ubuntu0.1",
"1:4.1.48-4+deb11u2ubuntu0.1+esm1",
"1:4.1.48-4+deb11u2ubuntu0.1+esm3",
"1:4.1.48-4+deb11u2ubuntu0.2",
"1:4.1.48-4+deb11u2ubuntu0.2+esm1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libnetty-java",
"binary_version": "1:4.1.48-9ubuntu0.2+esm1"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:24.04:LTS",
"name": "netty",
"purl": "pkg:deb/ubuntu/netty@1:4.1.48-9ubuntu0.2+esm1?arch=source\u0026distro=esm-apps/noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:4.1.48-7",
"1:4.1.48-8",
"1:4.1.48-9",
"1:4.1.48-9ubuntu0.1~esm1",
"1:4.1.48-9ubuntu0.1~esm2",
"1:4.1.48-9ubuntu0.1",
"1:4.1.48-9ubuntu0.1+esm1",
"1:4.1.48-9ubuntu0.1+esm3",
"1:4.1.48-9ubuntu0.2",
"1:4.1.48-9ubuntu0.2+esm1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libnetty-buffer-java",
"binary_version": "1:4.1.48-16ubuntu0.1~esm2"
},
{
"binary_name": "libnetty-common-java",
"binary_version": "1:4.1.48-16ubuntu0.1~esm2"
},
{
"binary_name": "libnetty-java",
"binary_version": "1:4.1.48-16ubuntu0.1~esm2"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:26.04:LTS",
"name": "netty",
"purl": "pkg:deb/ubuntu/netty@1:4.1.48-16ubuntu0.1~esm2?arch=source\u0026distro=esm-apps/resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:4.1.48-10",
"1:4.1.48-11",
"1:4.1.48-12",
"1:4.1.48-13",
"1:4.1.48-14",
"1:4.1.48-16",
"1:4.1.48-16ubuntu0.1~esm2"
]
}
],
"aliases": [],
"details": "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.",
"id": "UBUNTU-CVE-2026-75596",
"modified": "2026-08-21T00:00:00Z",
"published": "2026-08-21T00:00:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-75596"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-75596"
},
{
"type": "REPORT",
"url": "https://github.com/netty/netty/security/advisories/GHSA-fccg-mwvh-qqg4"
},
{
"type": "REPORT",
"url": "https://github.com/netty/netty/pull/17213"
},
{
"type": "REPORT",
"url": "https://github.com/netty/netty/pull/17217"
},
{
"type": "REPORT",
"url": "https://github.com/netty/netty/commit/1b5abc6443b63726c72cdd285af2feb7ddbb8ff7"
},
{
"type": "REPORT",
"url": "https://github.com/netty/netty/commit/9e0519239108a69b7e9bbc5e9182ee139a0d7961"
},
{
"type": "REPORT",
"url": "https://github.com/netty/netty/releases/tag/netty-4.1.137.Final"
},
{
"type": "REPORT",
"url": "https://github.com/netty/netty/releases/tag/netty-4.2.17.Final"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "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",
"type": "CVSS_V4"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2026-75596"
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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