ImpactThe undici WebSocket client is vulnerable to a denial-of-service attack due to improper validation of the servermaxwindowbits parameter in the permessage-deflate extension. When a WebSocket client connects to a server, it automatically advertises support for permessage-deflate compression. A malicious server can respond with an out-of-range servermaxwindowbits value (outside zlib's valid range of 8-15). When the server subsequently sends a compressed frame, the client attempts to create a zlib InflateRaw instance with the invalid windowBits value, causing a synchronous RangeError exception that is not caught, resulting in immediate process termination.
The vulnerability exists because:
{
"cna_assigner": "openjs",
"unresolved_ranges": [
{
"source": "AFFECTED_FIELD",
"extracted_events": [
{
"last_affected": "< 6.24.0; 7.0.0 < 7.24.0"
}
]
}
],
"cwe_ids": [
"CWE-1284",
"CWE-248"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/2xxx/CVE-2026-2229.json"
}{
"cpe": "cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:*",
"source": "CPE_RANGE",
"extracted_events": [
{
"introduced": "0"
},
{
"fixed": "6.24.0"
},
{
"introduced": "7.0.0"
},
{
"fixed": "7.24.0"
}
]
}