{"id":"CVE-2026-126408","kind":"vulnerability","aliases":["CVE-2026-126408"],"related":[],"title":"Wasmtime: type-check gap lets a guest module crash the host","description":"Wasmtime 47.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 contains an insufficient type-check in the TypedFunc embedder API for I31, Option<I31>, and Option<NoneRef> parameter or result types, reaching an unreachable!() path. A malicious guest module exporting a function that uses another anyref-hierarchy type can panic the host embedding, causing denial of service.","summary":"Wasmtime's TypedFunc embedder API fails to type-check I31 and Option<NoneRef> parameters and results, reaching an unreachable!() path. A malicious WebAssembly guest module can make the host embedding panic, causing denial of service.","severity":"low","cvss":1.8,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["package","rust","wasmtime","webassembly"],"not_affected_if":["no-embedding","trusted-modules-only"],"how_to_check":"- Check the Wasmtime version in your dependency manifest (for example `Cargo.lock`) and compare it with the fixed versions below.\n- Look for embedders that load untrusted guest modules and call functions through the TypedFunc API with anyref-hierarchy types.","fix":"- `48.0.8` for the 47.x and 48.x line before the fix\n- `49.0.5` for the 49.x line\n- `50.0.1` for the 50.x line","status":"open","published_at":"2026-11-13T10:17:45+00:00","first_seen_at":"2026-11-13T10:47:20+00:00","triaged_at":"2026-11-13T10:59:05+00:00","updated_at":"2026-11-13T10:59:05+00:00","category":"package","confidence":0.7,"triage":{"at":"2026-11-13T10:59:05Z","model":"claude-haiku-5-5","output":{"fix":"- `48.0.8` for the 47.x and 48.x line before the fix\n- `49.0.5` for the 49.x line\n- `50.0.1` for the 50.x line","reach":"unknown","title":"Wasmtime: type-check gap lets a guest module crash the host","impact":"low","summary":"Wasmtime's TypedFunc embedder API fails to type-check I31 and Option<NoneRef> parameters and results, reaching an unreachable!() path. A malicious WebAssembly guest module can make the host embedding panic, causing denial of service.","audience":"developers","category":"package","nicknames":[],"who_cares":["wasmtime","rust","webassembly"],"confidence":0.7,"fix_status":"available","needs_auth":"no","worst_case":"Host embedding panics, causing denial of service","analyst_note":"","how_to_check":"- Check the Wasmtime version in your dependency manifest (for example `Cargo.lock`) and compare it with the fixed versions below.\n- Look for embedders that load untrusted guest modules and call functions through the TypedFunc API with anyref-hierarchy types.","plain_action":"","product_name":"","needs_analyst":false,"not_affected_if":["trusted-modules-only","no-embedding"],"who_is_affected":"Applications that embed Wasmtime and run untrusted WebAssembly guest modules are exposed, because a malicious guest can panic the host process. Programs that only run trusted modules or do not embed Wasmtime can skip it.","user_interaction":"no","product_ecosystem":"","needs_special_setup":"unknown","severity_if_unknown":"low"},"cost_usd":0.000742,"input_tokens":4674,"output_tokens":550,"severity_before":"low"},"analyst_status":null,"analyst_note":null,"search":"'-126408':15A,18A '-2026':14A,17A '47.0.0':59C '48.0.8':61C '49.0.0':62C '49.0.5':64C '50.0.0':66C '50.0.1':68C 'anoth':102C 'anyref':104C 'anyref-hierarchi':103C 'api':27B,79C 'caus':54B,112C 'check':4A,32B,74C 'contain':69C 'crash':10A 'cve':13A,16A 'denial':55B,113C 'embed':52B,111C 'embedd':26B,78C 'export':97C 'fail':28B 'function':99C 'gap':5A 'guest':8A,46B,95C 'hierarchi':105C 'host':12A,51B,110C 'i31':33B,81C 'insuffici':71C 'let':6A 'make':49B 'malici':44B,94C 'modul':9A,47B,96C 'option':35B,82C,84C 'packag':19B 'panic':53B,108C 'paramet':36B,85C 'path':42B,92C 'reach':39B,89C 'result':38B,87C 'rust':20B 'servic':57B,115C 'type':3A,31B,73C,88C,106C 'type-check':2A,30B,72C 'typedfunc':25B,77C 'unreach':41B,91C 'use':101C 'wasmtim':1A,21B,23B,58C 'webassembl':22B,45B","nicknames":[],"mitigations":[],"who_affected":"Applications that embed Wasmtime and run untrusted WebAssembly guest modules are exposed, because a malicious guest can panic the host process. Programs that only run trusted modules or do not embed Wasmtime can skip it.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"developers","plain_action":null,"pkeys":[],"ptokens":[],"labels":["low","package","rust","wasmtime","webassembly"],"campaign_type":null,"search_a":"'-126408':15A,18A '-2026':14A,17A 'check':4A 'crash':10A 'cve':13A,16A 'gap':5A 'guest':8A 'host':12A 'let':6A 'modul':9A 'type':3A 'type-check':2A 'wasmtim':1A","search_b":"'api':27B 'caus':54B 'check':32B 'denial':55B 'embed':52B 'embedd':26B 'fail':28B 'guest':46B 'host':51B 'i31':33B 'make':49B 'malici':44B 'modul':47B 'option':35B 'packag':19B 'panic':53B 'paramet':36B 'path':42B 'reach':39B 'result':38B 'rust':20B 'servic':57B 'type':31B 'type-check':30B 'typedfunc':25B 'unreach':41B 'wasmtim':21B,23B 'webassembl':22B,45B","search_c":"'47.0.0':59C '48.0.8':61C '49.0.0':62C '49.0.5':64C '50.0.0':66C '50.0.1':68C 'anoth':102C 'anyref':104C 'anyref-hierarchi':103C 'api':79C 'caus':112C 'check':74C 'contain':69C 'denial':113C 'embed':111C 'embedd':78C 'export':97C 'function':99C 'guest':95C 'hierarchi':105C 'host':110C 'i31':81C 'insuffici':71C 'malici':94C 'modul':96C 'option':82C,84C 'panic':108C 'paramet':85C 'path':92C 'reach':89C 'result':87C 'servic':115C 'type':73C,88C,106C 'type-check':72C 'typedfunc':77C 'unreach':91C 'use':101C 'wasmtim':58C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-10-29T19:06:09+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:A/AC:H/AT:P/PR:H/UI:P/VC:N/VI:N/VA:L/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-2026-126408","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-126408","severity":null,"published_at":"2026-11-13T10:17:45+00:00","modified_at":"2026-11-13T10:17:45+00:00","first_seen_at":"2026-11-13T10:47:20+00:00","fetched_at":"2026-11-13T10:47:20+00:00","note":null}],"documents":[{"id":145059,"url":"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-3982-jqvv-277m","title":"Vendor advisory: github.com","kind":"vendor","source":"nvd","publisher":"vendor","text":null,"published_at":"2026-10-29T19:06:09+00:00","relation":"advisory","confidence":null,"note":"Vendor advisory: github.com"},{"id":145060,"url":"https://www.vulncheck.com/advisories/wasmtime-47.0.0-before-48.0.8-denial-of-service-via-typedfunc-type-check-panic","title":"Third-party advisory: www.vulncheck.com","kind":"advisory","source":"nvd","publisher":"research","text":null,"published_at":null,"relation":"advisory","confidence":null,"note":"Third-party advisory: www.vulncheck.com"}],"disclosures":[],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}