GHSA-38RV-X7PX-6HHQ
Vulnerability from github – Published: 2026-06-18 14:28 – Updated: 2026-06-18 14:28Impact
The undici WebSocket client enforces maxPayloadSize per-frame but does not enforce the cumulative size of fragmented uncompressed messages. A malicious WebSocket server can stream many small fragments that each pass per-frame validation but collectively exceed the configured limit, causing unbounded memory growth in the client process. The result is memory exhaustion and a denial of service.
Affected applications are those using the undici WebSocket client (new WebSocket(...)) that can be induced to connect to an attacker-controlled or compromised WebSocket endpoint.
This is a regression specific to undici 8.1.0. The 6.25.0 line shipped the equivalent cumulative check from the start and is unaffected. The 7.x line never had the maxPayloadSize feature and is also unaffected.
Patches
Upgrade to undici >= 8.5.0.
Workarounds
No workaround is available. The fix must be applied through an upgrade.
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "undici"
},
"ranges": [
{
"events": [
{
"introduced": "8.0.0"
},
{
"fixed": "8.5.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-9675"
],
"database_specific": {
"cwe_ids": [
"CWE-400",
"CWE-770"
],
"github_reviewed": true,
"github_reviewed_at": "2026-06-18T14:28:10Z",
"nvd_published_at": "2026-06-17T17:17:28Z",
"severity": "HIGH"
},
"details": "## Impact\n\nThe undici WebSocket client enforces `maxPayloadSize` per-frame but does not enforce the cumulative size of fragmented uncompressed messages. A malicious WebSocket server can stream many small fragments that each pass per-frame validation but collectively exceed the configured limit, causing unbounded memory growth in the client process. The result is memory exhaustion and a denial of service.\n\nAffected applications are those using the undici WebSocket client (`new WebSocket(...)`) that can be induced to connect to an attacker-controlled or compromised WebSocket endpoint.\n\nThis is a regression specific to undici 8.1.0. The 6.25.0 line shipped the equivalent cumulative check from the start and is unaffected. The 7.x line never had the `maxPayloadSize` feature and is also unaffected.\n\n## Patches\n\nUpgrade to undici \u003e= 8.5.0.\n\n## Workarounds\n\nNo workaround is available. The fix must be applied through an upgrade.",
"id": "GHSA-38rv-x7px-6hhq",
"modified": "2026-06-18T14:28:10Z",
"published": "2026-06-18T14:28:10Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/nodejs/undici/security/advisories/GHSA-38rv-x7px-6hhq"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-9675"
},
{
"type": "WEB",
"url": "https://cna.openjsf.org/security-advisories.html"
},
{
"type": "PACKAGE",
"url": "https://github.com/nodejs/undici"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
],
"summary": "undici WebSocket client vulnerable to denial of service via cumulative fragment bypass"
}
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