CVE-2026-27195

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Starting with Wasmtime 39.0.0, the `component-model-async` feature became the default, which brought with it a new implementation of `[Typed]Func::call_async` which made it capable of calling async-typed guest export functions. However, that implementation had a bug leading to a panic under certain circumstances: First, the host embedding calls `[Typed]Func::call_async` on a function exported by a component, polling the returned `Future` once. Second, the component function yields control to the async runtime (e.g. Tokio), e.g. due to a call to host function registered using `LinkerInstance::func_wrap_async` which yields, or due an epoch interruption. Third, the host embedding drops the `Future` after polling it once. This leaves the component instance in a non-reenterable state since the call never had a chance to complete. Fourth, the host embedding calls `[Typed]Func::call_async` again, polling the returned `Future`. Since the component instance cannot be entered at this point, the call traps, but not before allocating a task and thread for the call. Fifth, the host embedding ignores the trap and drops the `Future`. This panics due to the runtime attempting to dispose of the task created above, which panics since the thread has not yet exited. When a host embedder using the affected versions of Wasmtime calls `wasmtime::component::[Typed]Func::call_async` on a guest export and then drops the returned future without waiting for it to resolve, and then does so again with the same component instance, Wasmtime will panic. Embeddings that have the `component-model-async` compile-time feature disabled are unaffected. Wasmtime 40.0.4 and 41.0.4 have been patched to fix this issue. Versions 42.0.0 and later are not affected. If an embedding is not actually using any component-model-async features then disabling the `component-model-async` Cargo feature can work around this issue. This issue can also be worked around by either ensuring every `call_async` future is awaited until it completes or refraining from using the `Store` again after dropping a not-yet-resolved `call_async` future."}], "source": {"advisory": "GHSA-xjhv-v822-pf94", "discovery": "UNKNOWN"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-02-24T21:36:45.787568Z", "id": "CVE-2026-27195", "options": [{"Exploitation": "poc"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-02-24T21:36:54.122Z"}}]}}

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Starting with Wasmtime 39.0.0, the `component-model-async` feature became the default, which brought with it a new implementation of `[Typed]Func::call_async` which made it capable of calling async-typed guest export functions. However, that implementation had a bug leading to a panic under certain circumstances: First, the host embedding calls `[Typed]Func::call_async` on a function exported by a component, polling the returned `Future` once. Second, the component function yields control to the async runtime (e.g. Tokio), e.g. due to a call to host function registered using `LinkerInstance::func_wrap_async` which yields, or due an epoch interruption. Third, the host embedding drops the `Future` after polling it once. This leaves the component instance in a non-reenterable state since the call never had a chance to complete. Fourth, the host embedding calls `[Typed]Func::call_async` again, polling the returned `Future`. Since the component instance cannot be entered at this point, the call traps, but not before allocating a task and thread for the call. Fifth, the host embedding ignores the trap and drops the `Future`. This panics due to the runtime attempting to dispose of the task created above, which panics since the thread has not yet exited. When a host embedder using the affected versions of Wasmtime calls `wasmtime::component::[Typed]Func::call_async` on a guest export and then drops the returned future without waiting for it to resolve, and then does so again with the same component instance, Wasmtime will panic. Embeddings that have the `component-model-async` compile-time feature disabled are unaffected. Wasmtime 40.0.4 and 41.0.4 have been patched to fix this issue. Versions 42.0.0 and later are not affected. If an embedding is not actually using any component-model-async features then disabling the `component-model-async` Cargo feature can work around this issue. 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Starting with Wasmtime 39.0.0, the `component-model-async` feature became the default, which brought with it a new implementation of `[Typed]Func::call_async` which made it capable of calling async-typed guest export functions. However, that implementation had a bug leading to a panic under certain circumstances: First, the host embedding calls `[Typed]Func::call_async` on a function exported by a component, polling the returned `Future` once. Second, the component function yields control to the async runtime (e.g. Tokio), e.g. due to a call to host function registered using `LinkerInstance::func_wrap_async` which yields, or due an epoch interruption. Third, the host embedding drops the `Future` after polling it once. This leaves the component instance in a non-reenterable state since the call never had a chance to complete. Fourth, the host embedding calls `[Typed]Func::call_async` again, polling the returned `Future`. Since the component instance cannot be entered at this point, the call traps, but not before allocating a task and thread for the call. Fifth, the host embedding ignores the trap and drops the `Future`. This panics due to the runtime attempting to dispose of the task created above, which panics since the thread has not yet exited. When a host embedder using the affected versions of Wasmtime calls `wasmtime::component::[Typed]Func::call_async` on a guest export and then drops the returned future without waiting for it to resolve, and then does so again with the same component instance, Wasmtime will panic. Embeddings that have the `component-model-async` compile-time feature disabled are unaffected. Wasmtime 40.0.4 and 41.0.4 have been patched to fix this issue. Versions 42.0.0 and later are not affected. If an embedding is not actually using any component-model-async features then disabling the `component-model-async` Cargo feature can work around this issue. This issue can also be worked around by either ensuring every `call_async` future is awaited until it completes or refraining from using the `Store` again after dropping a not-yet-resolved `call_async` future."}, {"lang": "es", "value": "Wasmtime es un entorno de ejecuci\u00f3n para WebAssembly. A partir de Wasmtime 39.0.0, la caracter\u00edstica 'component-model-async' se convirti\u00f3 en la predeterminada, lo que trajo consigo una nueva implementaci\u00f3n de '[Typed]Func::call_async' que la hizo capaz de llamar a funciones de exportaci\u00f3n de invitado de tipo as\u00edncrono. Sin embargo, esa implementaci\u00f3n ten\u00eda un error que provocaba un p\u00e1nico bajo ciertas circunstancias: Primero, la incrustaci\u00f3n anfitriona llama a '[Typed]Func::call_async' en una funci\u00f3n exportada por un componente, sondeando la 'Future' devuelta una vez. Segundo, la funci\u00f3n del componente cede el control al entorno de ejecuci\u00f3n as\u00edncrono (por ejemplo, Tokio), por ejemplo, debido a una llamada a una funci\u00f3n anfitriona registrada usando 'LinkerInstance::func_wrap_async' que cede, o debido a una interrupci\u00f3n de \u00e9poca. Tercero, la incrustaci\u00f3n anfitriona descarta la 'Future' despu\u00e9s de sondearla una vez. Esto deja la instancia del componente en un estado no reentrante ya que la llamada nunca tuvo la oportunidad de completarse. Cuarto, la incrustaci\u00f3n anfitriona llama de nuevo a '[Typed]Func::call_async', sondeando la 'Future' devuelta. Dado que la instancia del componente no puede ser accedida en este punto, la llamada atrapa, pero no antes de asignar una tarea y un hilo para la llamada. Quinto, la incrustaci\u00f3n anfitriona ignora la trampa y descarta la 'Future'. Esto provoca un p\u00e1nico debido a que el entorno de ejecuci\u00f3n intenta disponer de la tarea creada anteriormente, lo que provoca un p\u00e1nico ya que el hilo a\u00fan no ha salido. Cuando un incrustador anfitri\u00f3n que utiliza las versiones afectadas de Wasmtime llama a 'wasmtime::component::[Typed]Func::call_async' en una exportaci\u00f3n de invitado y luego descarta la 'Future' devuelta sin esperar a que se resuelva, y luego lo hace de nuevo con la misma instancia del componente, Wasmtime entrar\u00e1 en p\u00e1nico. Las incrustaciones que tienen la caracter\u00edstica 'component-model-async' en tiempo de compilaci\u00f3n deshabilitada no se ven afectadas. Wasmtime 40.0.4 y 41.0.4 han sido parcheadas para solucionar este problema. Las versiones 42.0.0 y posteriores no se ven afectadas. Si una incrustaci\u00f3n no est\u00e1 utilizando realmente ninguna caracter\u00edstica de component-model-async, entonces deshabilitar la caracter\u00edstica Cargo 'component-model-async' puede solucionar este problema. Este problema tambi\u00e9n puede solucionarse asegurando que cada 'Future' de 'call_async' sea esperada hasta que se complete o absteni\u00e9ndose de usar el 'Store' de nuevo despu\u00e9s de descartar una 'Future' de 'call_async' a\u00fan no resuelta."}], "id": "CVE-2026-27195", "lastModified": "2026-06-17T10:26:49.743", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "HIGH", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 6.9, "baseSeverity": "MEDIUM", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "LOW", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "HIGH", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "PASSIVE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/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", "version": "4.0", "vulnAvailabilityImpact": "HIGH", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "security-advisories@github.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-27195", "options": [{"exploitation": "poc"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-02-24T21:36:45.787568Z", "version": "2.0.3"}}]}, "published": "2026-02-24T22:16:32.253", "references": [{"source": "security-advisories@github.com", "tags": ["Product"], "url": "https://bytecodealliance.zulipchat.com/#narrow/channel/206238-general/topic/.E2.9C.94.20Panic.20in.20Wasmtime.2041.2E0.2E3.20.28runtime.2Fconcurrent.2Fcomponent.29/with/574438798"}, {"source": "security-advisories@github.com", "tags": ["Patch"], "url": "https://github.com/bytecodealliance/wasmtime/commit/9e51c0d9a240a9613d279c061f82286bd11383fd"}, {"source": "security-advisories@github.com", "tags": ["Patch"], "url": "https://github.com/bytecodealliance/wasmtime/commit/d86b00736b9ece60b3c81e52f7a7e4cdd9f7d895"}, {"source": "security-advisories@github.com", "tags": ["Product", "Release Notes"], "url": "https://github.com/bytecodealliance/wasmtime/releases/tag/v40.0.4"}, {"source": "security-advisories@github.com", "tags": ["Product", "Release Notes"], "url": "https://github.com/bytecodealliance/wasmtime/releases/tag/v41.0.4"}, {"source": "security-advisories@github.com", "tags": ["Third Party Advisory"], "url": "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xjhv-v822-pf94"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-755"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

{"bugzilla": {"description": "wasmtime: Wasmtime: Denial of Service via repeated async function calls", "id": "2442481", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2442481"}, "csaw": false, "cvss3": {"cvss3_base_score": "4.7", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-248", "details": ["No description is available for this CVE."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability."}, "name": "CVE-2026-27195", "package_state": [{"cpe": "cpe:/a:redhat:connectivity_link:1", "fix_state": "Fix deferred", "package_name": "rhcl-1/wasm-shim-rhel9", "product_name": "Red Hat Connectivity Link 1"}], "public_date": "2026-02-24T21:15:20Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-27195\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-27195\nhttps://bytecodealliance.zulipchat.com/#narrow/channel/206238-general/topic/.E2.9C.94.20Panic.20in.20Wasmtime.2041.2E0.2E3.20.28runtime.2Fconcurrent.2Fcomponent.29/with/574438798\nhttps://github.com/bytecodealliance/wasmtime/commit/9e51c0d9a240a9613d279c061f82286bd11383fd\nhttps://github.com/bytecodealliance/wasmtime/commit/d86b00736b9ece60b3c81e52f7a7e4cdd9f7d895\nhttps://github.com/bytecodealliance/wasmtime/releases/tag/v40.0.4\nhttps://github.com/bytecodealliance/wasmtime/releases/tag/v41.0.4\nhttps://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xjhv-v822-pf94"], "threat_severity": "Moderate"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[39.0.0,40.0.4)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[41.0.0,41.0.4)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "wasmtime", "source": "cna", "vendor": "bytecodealliance"}, "product": "wasmtime", "vendor": "bytecodealliance"}], "analysis": {"en": {"generated_at": "2026-04-17T15:37:28.873031+00:00", "value": {"mitigation_remediation": ["Upgrade the Wasmtime library to version 40.0.4, 41.0.4, or any 42.0.0 and later release where the bug is fixed.", "If an upgrade is not feasible, explicitly disable the component-model-async Cargo feature when compiling Wasmtime to avoid the vulnerable path.", "Refactor host code to await the future returned by call_async before dropping it; ensure that all async component calls complete or are properly cancelled before re\u2011using the store.", "As a temporary measure, if the embedding never calls async component exports, remove any such calls or ensure they are not invoked after a dropped future."], "summary": {"action": "Patch Now", "impact": "Denial of Service (runtime crash)"}, "threat_synthesis": {"affected_systems": "The vulnerability affects all binary releases of Wasmtime starting with version 39.0.0 up to, but excluding, the patched releases 40.0.4, 41.0.4 and any later releases such as 42.0.0+, where the component-model-async feature defaults to its fixed implementation. Embeddings compiled without the component-model-async feature, or those that never invoke async component exports, are not impacted. The affected product is the Wasmtime runtime provided by Bytecode Alliance.", "description_and_impact": "The bug causes Wasmtime to panic when an embedding calls an async guest export, polls the returned future, then drops it before it resolves, and subsequently makes another async call using that component instance. Because the component has entered a non\u2011reenterable state, the second call traps, and the interim task thread is not yet terminated, leading to a panic during cleanup. This results in the host process crashing, which effectively denies service for any application embedding Wasmtime.", "risk_and_exploitability": "The CVSS score is 6.9, reflecting moderate severity, and the EPSS score is below 1%, indicating a very low probability that the flaw will be exploited in the wild. The vulnerability is not listed in CISA's KEV catalog. Exploitation requires an embedding that performs a call_async on a component-exported function, polls once, drops the future, then reuses the component instance to make another call, and continues to ignore the trapping error. Because this pattern is non\u2011obvious and likely internal to the embedding application, the attack surface is limited, but a software developer who writes or maintains the Wasmtime host code could trigger it unintentionally, leading to a denial\u2011of\u2011service condition."}}}}, "created": "2026-02-25T11:35:29.015550+00:00", "updated": "2026-04-17T15:45:15.896746+00:00", "vendors": ["bytecodealliance", "bytecodealliance$PRODUCT$wasmtime"]}