{"id":"CVE-2026-109932","kind":"vulnerability","aliases":["CVE-2026-109932","GHSA-9fm3-97px-rjf6"],"related":[],"title":"undici WebSocket client vulnerable to Denial of Service via unbounded automatic PONG buffering","description":"undici is an HTTP client library for Node.js. In versions 5.15.0 through 6.29.0, 7.0.0 through 7.30.0, and 8.0.0 through 8.12.1, its WebSocket client, including the bundled WebSocket exposed by Node.js, can be driven to exhaust process memory by a malicious or compromised WebSocket server. For every PING frame received, the client automatically writes a PONG response and ignores the backpressure signal from the socket write, so a server that streams small PING frames while never reading the client's PONGs makes the outbound write queue and heap grow without bound until the Node.js process runs out of memory and terminates. The attack is remote and unauthenticated, needs only a normal WebSocket connection, and is asymmetric, since small inbound PINGs produce a much larger retained outbound queue, with availability the only impact. The issue is fixed in undici 6.29.1, 7.30.1, and 8.12.2, which pause WebSocket frame parsing when the automatic PONG response hits socket backpressure and resume on drain, bounding the outbound queue, and users should upgrade to one of those versions or later. There is no workaround.","summary":"The undici WebSocket client, including Node.js's built-in globalThis.WebSocket, automatically answers every PING frame without respecting write backpressure. A malicious or compromised WebSocket server that sends small PINGs and never reads the PONGs makes the outbound queue grow until the process runs out of memory and crashes.","severity":"high","cvss":7.5,"epss":0.00321,"exploited":false,"exploited_at":null,"products":[{"name":"undici","fixed":["6.29.1"],"affected":">= 5.15.0, < 6.29.1","ecosystem":"npm"},{"name":"undici","fixed":["7.30.1"],"affected":">= 7.0.0, < 7.30.1","ecosystem":"npm"},{"name":"undici","fixed":["8.12.2"],"affected":">= 8.0.0, < 8.12.2","ecosystem":"npm"},{"name":"nodejs undici","fixed":["6.29.1"],"affected":">= 5.15.0, < 6.29.1","ecosystem":"vendor"},{"name":"nodejs undici","fixed":["7.30.1"],"affected":">= 7.0.0, < 7.30.1","ecosystem":"vendor"},{"name":"nodejs undici","fixed":["8.12.2"],"affected":">= 8.0.0, < 8.12.2","ecosystem":"vendor"}],"ecosystems":["npm","vendor"],"tags":["cwe-400","cwe-405","cwe-770","node.js","npm","package","undici","websocket-clients"],"not_affected_if":["no-websocket-client","trusted-servers-only"],"how_to_check":"- Run `node -p \"require('undici/package.json').version\"` in the project to see the installed undici version\n- Run `npm ls undici` to find every copy, including ones pulled in transitively\n- Check whether the app opens WebSocket connections to servers it does not fully control, via `globalThis.WebSocket` or `new WebSocket(` in the code","fix":"- Upgrade undici to `6.29.1` on the 6.x line, `7.30.1` on the 7.x line, or `8.12.2` on the 8.x line\n- Upgrade Node.js to a release that bundles a fixed undici, if the app relies on the built-in `globalThis.WebSocket`\n- No workaround is documented by the sources","status":"open","published_at":"2026-10-15T19:17:22+00:00","first_seen_at":"2026-10-27T19:04:56+00:00","triaged_at":"2026-10-27T19:05:56+00:00","updated_at":"2026-10-27T19:33:18+00:00","category":"package","confidence":0.8,"triage":{"at":"2026-10-27T19:05:56Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade undici to `6.29.1` on the 6.x line, `7.30.1` on the 7.x line, or `8.12.2` on the 8.x line\n- Upgrade Node.js to a release that bundles a fixed undici, if the app relies on the built-in `globalThis.WebSocket`\n- No workaround is documented by the sources","reach":"internet","title":"undici: WebSocket client lets a malicious server exhaust process memory","impact":"low","summary":"The undici WebSocket client, including Node.js's built-in globalThis.WebSocket, automatically answers every PING frame without respecting write backpressure. A malicious or compromised WebSocket server that sends small PINGs and never reads the PONGs makes the outbound queue grow until the process runs out of memory and crashes.","category":"package","nicknames":[],"who_cares":["node.js","undici","websocket-clients","npm"],"confidence":0.8,"needs_auth":"no","worst_case":"remote server exhausts process memory and crashes the Node.js process","analyst_note":"","how_to_check":"- Run `node -p \"require('undici/package.json').version\"` in the project to see the installed undici version\n- Run `npm ls undici` to find every copy, including ones pulled in transitively\n- Check whether the app opens WebSocket connections to servers it does not fully control, via `globalThis.WebSocket` or `new WebSocket(` in the code","needs_analyst":false,"not_affected_if":["no-websocket-client","trusted-servers-only"],"who_is_affected":"Applications that open WebSocket connections with undici or Node.js's built-in WebSocket client to servers that could be malicious or compromised are exposed. Versions from 5.15.0 onward are affected across the 5.x, 6.x, 7.x and 8.x lines, within the listed ranges. Services that use WebSockets only with trusted, fully controlled servers, or that do not use the WebSocket client at all, face much less risk.","user_interaction":"no","needs_special_setup":"no","severity_if_unknown":"medium"},"cost_usd":0.000728,"input_tokens":3739,"output_tokens":709,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-109932':16A,24A '-2026':15A,23A '-400':35B '-405':37B '-770':39B '5.15.0':106C '6.29.0':108C '6.29.1':233C '7.0.0':109C '7.30.0':111C '7.30.1':234C '8.0.0':113C '8.12.1':115C '8.12.2':236C '97px':20A '9fm3':19A 'answer':59B 'asymmetr':210C 'attack':197C 'automat':11A,58B,147C,244C 'avail':223C 'backpressur':66B,155C,249C 'bound':185C,254C 'buffer':13A 'built':55B 'built-in':54B 'bundl':121C 'client':3A,46B,50B,100C,118C,146C,173C 'compromis':70B,137C 'connect':207C 'crash':95B 'cve':14A,22A 'cwe':34B,36B,38B 'denial':6A 'drain':253C 'driven':128C 'everi':60B,141C 'exhaust':130C 'expos':123C 'fix':230C 'frame':62B,143C,168C,240C 'ghsa':18A 'ghsa-9fm3-97px-rjf6':17A 'globalthis.websocket':57B 'grow':86B,183C 'heap':182C 'hit':247C 'http':99C 'ignor':153C 'impact':226C 'inbound':213C 'includ':51B,119C 'issu':228C 'larger':218C 'later':268C 'librari':101C 'make':82B,176C 'malici':68B,135C 'memori':93B,132C,193C 'much':217C 'need':202C 'never':78B,170C 'node.js':40B,52B,103C,125C,188C 'nodejs':28A,30A,32A 'normal':205C 'npm':41B 'one':263C 'outbound':84B,178C,220C,256C 'packag':42B 'pars':241C 'paus':238C 'ping':61B,76B,142C,167C,214C 'pong':12A,81B,150C,175C,245C 'process':89B,131C,189C 'produc':215C 'queue':85B,180C,221C,257C 'read':79B,171C 'receiv':144C 'remot':199C 'respect':64B 'respons':151C,246C 'resum':251C 'retain':219C 'rjf6':21A 'run':90B,190C 'send':74B 'server':72B,139C,163C 'servic':8A 'signal':156C 'sinc':211C 'small':75B,166C,212C 'socket':159C,248C 'stream':165C 'termin':195C 'unauthent':201C 'unbound':10A 'undici':1A,25A,26A,27A,29A,31A,33A,43B,48B,96C,232C 'upgrad':261C 'user':259C 'version':105C,266C 'via':9A 'vulner':4A 'websocket':2A,45B,49B,71B,117C,122C,138C,206C,239C 'websocket-cli':44B 'without':63B,184C 'workaround':272C 'write':65B,148C,160C,179C","nicknames":[],"mitigations":[],"who_affected":"Applications that open WebSocket connections with undici or Node.js's built-in WebSocket client to servers that could be malicious or compromised are exposed. Versions from 5.15.0 onward are affected across the 5.x, 6.x, 7.x and 8.x lines, within the listed ranges. Services that use WebSockets only with trusted, fully controlled servers, or that do not use the WebSocket client at all, face much less risk.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-15T19:17:22+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","cvss_by":"GitHub","poc_count":0,"sources":[{"source":"ghsa","external_id":"GHSA-9fm3-97px-rjf6","url":"https://github.com/advisories/GHSA-9fm3-97px-rjf6","severity":"medium","published_at":"2026-10-27T19:02:15+00:00","modified_at":"2026-10-27T19:02:17+00:00","first_seen_at":"2026-10-27T19:04:56+00:00","fetched_at":"2026-10-27T19:04:56+00:00","note":null},{"source":"nvd","external_id":"CVE-2026-109932","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-109932","severity":null,"published_at":"2026-10-15T19:17:22+00:00","modified_at":"2026-10-19T20:44:42+00:00","first_seen_at":"2026-10-27T19:33:18+00:00","fetched_at":"2026-10-27T19:33:18+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}