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CVE-2026-2229 is a denial-of-service vulnerability in the undici WebSocket client caused by improper validation of the permessage-deflate extension parameter server_max_window_bits. During WebSocket negotiation, the client advertises support for permessage-deflate compression. A malicious server can reply with a server_max_window_bits value outside zlib's valid range of 8 through 15. The vulnerable validation logic accepts digit-only input without enforcing the allowed numeric range, and the subsequent InflateRaw initialization is performed without exception handling. When the server then sends a compressed WebSocket frame, the client attempts to create a zlib InflateRaw instance with the invalid windowBits value, triggering a synchronous RangeError that propagates uncaught and terminates the Node.js process.
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No public exploit code observed for this vulnerability.
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26 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A denial-of-service vulnerability in undici via an invalid WebSocket permessage-deflate extension parameter.
A denial-of-service vulnerability in Undici caused by an invalid WebSocket permessage-deflate extension parameter.
A denial of service vulnerability in Undici triggered by an invalid WebSocket permessage-deflate extension parameter.
A denial of service vulnerability in Undici triggered by an invalid WebSocket permessage-deflate extension parameter.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.