{"id":"CVE-2026-119135","kind":"vulnerability","aliases":["CVE-2026-119135"],"related":[],"title":"Wasmtime: type mismatch on component stream read crashes the host process","description":"Wasmtime 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 panics when the host reads a component model stream as a different Rust item type than it was created with, because the host-to-host read path asserts matching TypeIds instead of returning an error. Guest code can return a host-created StreamReader<U> that the embedder reads as StreamReader<T>, where both types map to the same component model type, crashing the embedding process.","summary":"Wasmtime versions 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 panic when the host reads a component model stream as a different Rust type than it was created with. Guest code can trigger this by returning a host-created stream that the embedder reads with a mismatched type, crashing the embedding process.","severity":"medium","cvss":5.9,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["embedders","runtime","rust","wasmtime","webassembly"],"not_affected_if":["no-component-model-streams","trusted-guests-only","wasmtime-cli-only"],"how_to_check":null,"fix":"- Upgrade Wasmtime 46.x to `48.0.6` or later\n- Upgrade Wasmtime 49.x to `49.0.3` or later","status":"open","published_at":"2026-10-29T16:18:06+00:00","first_seen_at":"2026-10-29T16:25:58+00:00","triaged_at":"2026-10-29T16:31:41+00:00","updated_at":"2026-10-29T16:31:41+00:00","category":"runtime","confidence":0.7,"triage":{"at":"2026-10-29T16:31:41Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade Wasmtime 46.x to `48.0.6` or later\n- Upgrade Wasmtime 49.x to `49.0.3` or later","reach":"unknown","title":"Wasmtime: type mismatch on component stream read crashes the host process","impact":"low","summary":"Wasmtime versions 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 panic when the host reads a component model stream as a different Rust type than it was created with. Guest code can trigger this by returning a host-created stream that the embedder reads with a mismatched type, crashing the embedding process.","audience":"businesses","category":"runtime","nicknames":[],"who_cares":["wasmtime","rust","webassembly","embedders"],"confidence":0.7,"fix_status":"available","needs_auth":"unknown","worst_case":"Embedding process crashes from a panic, causing denial of service","analyst_note":"","how_to_check":"- Check the Wasmtime version in your Cargo.lock or dependency tree, e.g. `cargo tree -i wasmtime`\n- Look for embedders that run untrusted guest components and read component model streams from the host\n- Confirm whether the version is in the 46.0.0 to 48.0.5 range or the 49.0.0 to 49.0.2 range","plain_action":"","needs_analyst":false,"not_affected_if":["wasmtime-cli-only","no-component-model-streams","trusted-guests-only"],"who_is_affected":"Only applications that embed Wasmtime and read component model streams from the host, where guest code can return a host-created stream. Standalone CLI use and embedders that do not use streams with mismatched types are less exposed. The crash is a denial of service in the embedding process rather than code execution, as far as the sources state.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"medium"},"cost_usd":0.000744,"input_tokens":4185,"output_tokens":650,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-119135':14A,17A '-2026':13A,16A '46.0.0':25B,76C '48.0.6':27B,78C '49.0.0':29B,80C '49.0.3':31B,82C 'assert':111C 'code':52B,120C 'compon':5A,38B,89C,141C 'crash':8A,71B,144C 'creat':49B,61B,101C,126C 'cve':12A,15A 'differ':43B,94C 'embed':73B,146C 'embedd':18B,65B,130C 'error':118C 'guest':51B,119C 'host':10A,35B,60B,86C,106C,108C,125C 'host-creat':59B,124C 'host-to-host':105C 'instead':114C 'item':96C 'map':137C 'match':112C 'mismatch':3A,69B 'model':39B,90C,142C 'panic':32B,83C 'path':110C 'process':11A,74B,147C 'read':7A,36B,66B,87C,109C,131C 'return':57B,116C,122C 'runtim':19B 'rust':20B,44B,95C 'stream':6A,40B,62B,91C 'streamread':127C,133C 'trigger':54B 'type':2A,45B,70B,97C,136C,143C 'typeid':113C 'version':24B 'wasmtim':1A,21B,23B,75C 'webassembl':22B","nicknames":[],"mitigations":[],"who_affected":"Only applications that embed Wasmtime and read component model streams from the host, where guest code can return a host-created stream. Standalone CLI use and embedders that do not use streams with mismatched types are less exposed. The crash is a denial of service in the embedding process rather than code execution, as far as the sources state.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"first_public_at":"2026-10-29T16:18:06+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-2026-119135","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-119135","severity":null,"published_at":"2026-10-29T16:18:06+00:00","modified_at":"2026-10-29T16:18:06+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"}