{"id":"CVE-2026-119140","kind":"vulnerability","aliases":["CVE-2026-119140"],"related":[],"title":"Wasmtime: malicious component can crash host via thread.yield","description":"Wasmtime 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 contains a denial of service vulnerability that allows malicious components to panic the host via thread.yield in start functions. Attackers can supply a component whose start function calls an async-lowered import then thread.yield, causing an undisposed fiber drop that crashes embedders.","summary":"Wasmtime versions 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 let a malicious WebAssembly component panic the host process through thread.yield in a start function. The attacker only gets a denial of service that crashes applications embedding Wasmtime.","severity":"medium","cvss":5.9,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["embedders","runtime","rust","wasmtime","webassembly"],"not_affected_if":["fixed-version","trusted-components-only"],"how_to_check":"- Check the Wasmtime version in your dependencies, for example `wasmtime --version` or the wasmtime entry in Cargo.lock.\n- Look for embedders that load untrusted components and call their start functions.","fix":"- Wasmtime `48.0.6`\n- Wasmtime `49.0.3`","status":"open","published_at":"2026-10-29T16:18:07+00:00","first_seen_at":"2026-10-29T16:25:58+00:00","triaged_at":"2026-10-29T16:31:35+00:00","updated_at":"2026-10-29T16:31:35+00:00","category":"runtime","confidence":0.7,"triage":{"at":"2026-10-29T16:31:35Z","model":"claude-haiku-5-5","output":{"fix":"- Wasmtime `48.0.6`\n- Wasmtime `49.0.3`","reach":"unknown","title":"Wasmtime: malicious component can crash host via thread.yield","impact":"low","summary":"Wasmtime versions 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 let a malicious WebAssembly component panic the host process through thread.yield in a start function. The attacker only gets a denial of service that crashes applications embedding Wasmtime.","audience":"developers","category":"runtime","nicknames":[],"who_cares":["wasmtime","rust","webassembly","embedders"],"confidence":0.7,"fix_status":"available","needs_auth":"no","worst_case":"host process crashes, causing denial of service to the embedding application","analyst_note":"","how_to_check":"- Check the Wasmtime version in your dependencies, for example `wasmtime --version` or the wasmtime entry in Cargo.lock.\n- Look for embedders that load untrusted components and call their start functions.","plain_action":"","needs_analyst":false,"not_affected_if":["trusted-components-only","fixed-version"],"who_is_affected":"Applications that embed Wasmtime 46.0.0 to 48.0.5 or 49.0.0 to 49.0.2 and run WebAssembly components supplied by untrusted parties are exposed. A component whose start function calls an async-lowered import and then thread.yield can crash the host. Teams running only trusted components or on the fixed versions can skip it.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"medium"},"cost_usd":0.000699,"input_tokens":4162,"output_tokens":565,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-119140':11A,14A '-2026':10A,13A '46.0.0':22B,58C '48.0.6':24B,60C '49.0.0':26B,62C '49.0.3':28B,64C 'allow':72C 'applic':54B 'async':95C 'async-low':94C 'attack':45B,84C 'call':92C 'caus':100C 'compon':3A,33B,74C,88C 'contain':65C 'crash':5A,53B,106C 'cve':9A,12A 'denial':49B,67C 'drop':104C 'embed':55B 'embedd':15B,107C 'fiber':103C 'function':43B,83C,91C 'get':47B 'host':6A,36B,78C 'import':97C 'let':29B 'lower':96C 'malici':2A,31B,73C 'panic':34B,76C 'process':37B 'runtim':16B 'rust':17B 'servic':51B,69C 'start':42B,82C,90C 'suppli':86C 'thread.yield':8A,39B,80C,99C 'undispos':102C 'version':21B 'via':7A,79C 'vulner':70C 'wasmtim':1A,18B,20B,56B,57C 'webassembl':19B,32B 'whose':89C","nicknames":[],"mitigations":[],"who_affected":"Applications that embed Wasmtime 46.0.0 to 48.0.5 or 49.0.0 to 49.0.2 and run WebAssembly components supplied by untrusted parties are exposed. A component whose start function calls an async-lowered import and then thread.yield can crash the host. Teams running only trusted components or on the fixed versions can skip it.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"developers","plain_action":null,"first_public_at":"2026-10-29T16:18:07+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","cvss_by":"disclosure@vulncheck.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-119140","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-119140","severity":null,"published_at":"2026-10-29T16:18:07+00:00","modified_at":"2026-10-29T16:18:07+00:00","first_seen_at":"2026-10-29T16:25:58+00:00","fetched_at":"2026-10-29T16:25:58+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"}