CVE-2026-126408

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, and Option parameter or result types, reaching an unreachable! path. A malicious guest module exporting a function that uses another...

CVE-2026-126407

Wasmtime before 36.0.20, 37.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 allocates untracked host memory when a component receives a borrow of a resource it defines itself, bypassing the per-store handle limit. A malicious guest component can repeatedly transfer such borrowed...

CVE-2026-126406

The wasmtime-wasi-http p2 implementation in Wasmtime is vulnerable to HTTP Request Smuggling . Affected versions include prior to 36.0.20 , 37.0.0 before 48.0.8 , 49.0.0 before 49.0.5 , and 50.0.0 before 50.0.1 . The root cause is the ability of the component to send outgoing requests with confli...

EUVD-2026-125159

The wasmtime-wasi-http p2 implementation in Wasmtime before 36.0.20, 37.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 can send conflicting content-length headers, or ones not matching the body, in outgoing requests. A guest that reuses a received response's headers resource to...

EUVD-2026-125036

Wasmtime before 36.0.20, 37.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 allocates untracked host memory when a component receives a borrow of a resource it defines itself, bypassing the per-store handle limit. A malicious guest component can repeatedly transfer such borrowed...

CVE-2026-126407 Wasmtime before 36.0.20 Denial of Service via Borrowed Resource Transfer

Wasmtime before 36.0.20, 37.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 allocates untracked host memory when a component receives a borrow of a resource it defines itself, bypassing the per-store handle limit. A malicious guest component can repeatedly transfer such borrowed...

CVE-2026-126407

The Wasmtime runtime is vulnerable to a Denial of Service (DoS) attack in versions before 36.0.20, 37.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1. The root cause is that the engine allocates untracked host memory when a component receives a borrow of a resource it defined it...

CVE-2026-126408 Wasmtime 47.0.0 before 48.0.8 Denial of Service via TypedFunc Type-Check Panic

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, and Option parameter or result types, reaching an unreachable! path. A malicious guest module exporting a function that uses another...

CVE-2026-126408

The Wasmtime runtime versions 47.0.0 before 48.0.8 , 49.0.0 before 49.0.5 , and 50.0.0 before 50.0.1 are vulnerable to a Denial of Service (DoS) condition. The root cause is an insufficient type-check within the TypedFunc embedder API for specific parameter or result types, including I31 , Option...

CVE-2026-126409

Wasmtime versions 47.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 are vulnerable to a cross-engine type confusion issue. The root cause is that the StructType::with_finality_and_supertype function fails to verify that a supplied supertype belongs to the same Engine . This all...

EUVD-2026-125035

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, and Option parameter or result types, reaching an unreachable! path. A malicious guest module exporting a function that uses another...

EUVD-2026-125034

Wasmtime 47.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 contains a cross-engine type confusion vulnerability because StructType::withfinalityandsupertype does not validate that the supplied supertype belongs to the same Engine. Embedders using multiple engines that create a ...

CVE-2026-126410

The wasmtime-wasi crate in Wasmtime versions 48.0.0 before 48.0.8 , 49.0.0 before 49.0.5 , and 50.0.0 before 50.0.1 is vulnerable to a time-of-check/time-of-use (TOCTOU) race condition. The flaw exists in the wasip3 wasi:sockets udp-socket host implementation, allowing a malicious guest to bypass...

EUVD-2026-125033

Wasmtime's wasmtime-wasi crate 48.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 contains a time-of-check/time-of-use race in the wasip3 wasi:sockets udp-socket host implementation that lets guests bypass socketaddrcheck send restrictions. A malicious guest can race...

CVE-2026-121440

A flaw was found in Wasmtime. When processing HTTP traffic via the WebAssembly System Interface WASI, the runtime fails to validate forwarded HTTP trailers against forbidden header filtering rules. A WebAssembly guest application can exploit this vulnerability by forwarding a request or response...

CVE-2026-121441

A flaw was found in Wasmtime's wasi-http component. A malicious WebAssembly Wasm guest application can set multiple conflicting Content-Length headers on outgoing HTTP requests. This flaw allows an attacker to perform HTTP request smuggling through downstream servers or intermediaries that do not...

CVE-2026-121439

A flaw was found in wasmtime. The wasi-http component fails to properly validate Content-Length headers when processing network responses. A malicious WebAssembly guest can supply an invalid Content-Length header and splice response bodies, allowing HTTP Hypertext Transfer Protocol response...

CVE-2026-121441

Wasmtime before 36.0.19, 37.0.0 before 48.0.7, and 49.0.0 before 49.0.4 contains a request smuggling vulnerability in wasi-http that allows guests to set multiple conflicting content-length headers. Malicious guests can make the host send HTTP requests with conflicting content-length values to...

CVE-2026-121440

Wasmtime 46.0.0 before 48.0.7 and 49.0.0 before 49.0.4 fails to check forwarded trailers against the WasiHttpHooks::isforbiddenheader hook in wasi-http p3. WASIp3 guests can forward a request or response body so its trailers skip embedder-customized forbidden header filtering, undermining header...

CVE-2026-121439

Wasmtime 46.0.0 before 48.0.7 and 49.0.0 before 49.0.4 contains a response splitting vulnerability in wasi-http p3 that allows guests to set unvalidated content-length headers. Malicious wasip3 guests can splice an existing body into a new response with an incorrect content-length to perform...