undici is vulnerable to Unhandled Exception in undici WebSocket Client Due to Invalid server_max_window_bits Validation
ImpactThe undici WebSocket client is vulnerable to a denial-of-service attack due to improper validation of the server_max_window_bits 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 server_max_window_bits 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: * The isValidClientWindowBits() function only validates that the value contains ASCII digits, not that it falls within the valid range 8-15 * The createInflateRaw() call is not wrapped in a try-catch block * The resulting exception propagates up through the call stack and crashes the Node.js process
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-2229
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 3 Nov 2026, 17:58 UTC · Revision 1
Source evidence
undici is vulnerable to Unhandled Exception in undici WebSocket Client Due to Invalid server_max_window_bits Validation
core-osv · Original sourcePublished 12 Mar 2026, 20:27 UTC
ImpactThe undici WebSocket client is vulnerable to a denial-of-service attack due to improper validation of the server_max_window_bits 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 server_max_window_bits 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: * The isValidClientWindowBits() function only validates that the value contains ASCII digits, not that it falls within the valid range 8-15 * The createInflateRaw() call is not wrapped in a try-catch block * The resulting exception propagates up through the call stack and crashes the Node.js process
osv:CVE-2026-2229
Complete source record
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"method": "structured",
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"title": "undici is vulnerable to Unhandled Exception in undici WebSocket Client Due to Invalid server_max_window_bits Validation",
"summary": "ImpactThe undici WebSocket client is vulnerable to a denial-of-service attack due to improper validation of the server_max_window_bits 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 server_max_window_bits 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: * The isValidClientWindowBits() function only validates that the value contains ASCII digits, not that it falls within the valid range 8-15 * The createInflateRaw() call is not wrapped in a try-catch block * The resulting exception propagates up through the call stack and crashes the Node.js process",
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"modified": "2026-10-28T02:30:31.042897469Z",
"provider": "osv",
"references": [
"https://datatracker.ietf.org/doc/html/rfc7692",
"https://github.com/nodejs/undici/",
"https://hackerone.com/reports/3487486",
"https://nodejs.org/api/zlib.html#class-zlibinflateraw",
"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-2229.json",
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"https://access.redhat.com/errata/RHSA-2026:17789",
"https://access.redhat.com/errata/RHSA-2026:21772",
"https://access.redhat.com/errata/RHSA-2026:21931",
"https://access.redhat.com/errata/RHSA-2026:34342",
"https://access.redhat.com/errata/RHSA-2026:56431",
"https://access.redhat.com/errata/RHSA-2026:5807",
"https://access.redhat.com/errata/RHSA-2026:7080",
"https://access.redhat.com/errata/RHSA-2026:7123",
"https://access.redhat.com/errata/RHSA-2026:7302",
"https://access.redhat.com/errata/RHSA-2026:7310",
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"https://access.redhat.com/errata/RHSA-2026:7670",
"https://access.redhat.com/errata/RHSA-2026:7675",
"https://access.redhat.com/errata/RHSA-2026:7983",
"https://access.redhat.com/errata/RHSA-2026:9742",
"https://access.redhat.com/security/cve/CVE-2026-2229",
"https://cna.openjsf.org/security-advisories.html",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/2xxx/CVE-2026-2229.json",
"https://github.com/nodejs/undici/security/advisories/GHSA-v9p9-hfj2-hcw8",
"https://nvd.nist.gov/vuln/detail/CVE-2026-2229",
"https://bugzilla.redhat.com/show_bug.cgi?id=2447143"
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"source_id": "core-osv",
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"published_at": "2026-03-12T20:27:05.6+00:00"
}