50.0.0

Unreleased.

Added

• Add --listenfd option to wasmtime serve, which allows launching wasmtime
  with sockets inherited from a service manager (e.g. systemd socket units).

Changed

• Remove non-functional listenfd WASI CLI option.

Fixed

• Converting a borrowed Resource<T> or ResourceDynamic created with
  new_borrow into a ResourceAny outside of a component call no longer
  panics. The borrow is now lowered into the guest when the call happens, and
  ResourceAny::resource_drop is no longer required for such borrows.
  #7793

49.0.2

Released 2026-10-02.

Fixed

• WASI preview 0 implementation of poll_oneoff circumvents fuel consumption.
  GHSA-j366-h8gg-77pm

• Excessive allocated memory on the host when guests don't have stdio.
  GHSA-gqmc-89g8-p25r

• fd_readdir copies uninitialized struct padding into guest memory.
  GHSA-96f6-r43r-8c24

• Guest can panic host through filesystem timestamp before the epoch on wasip3.
  GHSA-mr2v-56j5-cmfc

• Wasmtime component async-lifted callback result count is unvalidated, causing a native stack buffer overflow.
  GHSA-32h6-97mm-8q3c

• Mis-typed WebAssembly tag imports can lead to GC heap corruption.
  GHSA-cfhf-m2cr-62wj

• Wasmtime wasi:http implementation panics with a zero timeout supplied.
  GHSA-w4qr-p94g-mjhv

• Rooting for GC values live across try_call may be missing, causing GC heap corruption.
  GHSA-hw8m-q44c-ggrf

48.0.5

Released 2026-10-02.

Fixed

• Fixed an issue where artifacts for 48.0.4 didn't get correctly published from
  CI and a GitHub release for 48.0.4 wasn't made.
  #14494

48.0.4

Released 2026-10-02.

Fixed

• WASI preview 0 implementation of poll_oneoff circumvents fuel consumption.
  GHSA-j366-h8gg-77pm

• Excessive allocated memory on the host when guests don't have stdio.
  GHSA-gqmc-89g8-p25r

• fd_readdir copies uninitialized struct padding into guest memory.
  GHSA-96f6-r43r-8c24

• Guest can panic host through filesystem timestamp before the epoch on wasip3.
  GHSA-mr2v-56j5-cmfc

• Wasmtime component async-lifted callback result count is unvalidated, causing a native stack buffer overflow.
  GHSA-32h6-97mm-8q3c

• Mis-typed WebAssembly tag imports can lead to GC heap corruption.
  GHSA-cfhf-m2cr-62wj

• Wasmtime wasi:http implementation panics with a zero timeout supplied.
  GHSA-w4qr-p94g-mjhv

• Rooting for GC values live across try_call may be missing, causing GC heap corruption.
  GHSA-hw8m-q44c-ggrf

36.0.17

Released 2026-10-02.

Fixed

• WASI preview 0 implementation of poll_oneoff circumvents fuel consumption.
  GHSA-j366-h8gg-77pm

• Excessive allocated memory on the host when guests don't have stdio.
  GHSA-gqmc-89g8-p25r

• fd_readdir copies uninitialized struct padding into guest memory.
  GHSA-96f6-r43r-8c24

49.0.1

Released 2026-09-24.

Fixed

• Do not drop fuel-spend accrued by callees of call_ref and callees that
  return via exception throws.
  GHSA-m63x-6p34-q65x

• Fix fuel spend for dynamic record lifting.
  GHSA-jqpg-j7w6-42pr

• Fix host memory exhaustion on outgoing HTTP body write.
  GHSA-c9gc-w9vx-w86p

• wasmtime-wasi: Fix panic on out-of-range datetimes in WASI filesystem set-times, set-times-at.
  GHSA-j2g9-4prp-pf6h

48.0.3

Released 2026-09-24.

Fixed

• Do not drop fuel-spend accrued by callees of call_ref and callees that
  return via exception throws.
  GHSA-m63x-6p34-q65x

• Fix fuel spend for dynamic record lifting.
  GHSA-jqpg-j7w6-42pr

• Fix host memory exhaustion on outgoing HTTP body write.
  GHSA-c9gc-w9vx-w86p

• wasmtime-wasi: Fix panic on out-of-range datetimes in WASI filesystem set-times, set-times-at.
  GHSA-j2g9-4prp-pf6h

36.0.16

Released 2026-09-24.

Fixed

• Fix fuel spend for dynamic record lifting.
  GHSA-jqpg-j7w6-42pr

• Fix host memory exhaustion on outgoing HTTP body write.
  GHSA-c9gc-w9vx-w86p

• wasmtime-wasi: Fix panic on out-of-range datetimes in WASI filesystem set-times, set-times-at.
  GHSA-j2g9-4prp-pf6h

49.0.0

Released 2026-09-21.

Added

• Winch now has initial experimental support for the WebAssembly
  exception-handling proposal.
  #14066
  #14081
  #14132
  #14149
  #14180
  #14209

• Wasmtime's type reflection APIs for WebAssembly GC types now have dedicated
  enums for Heap{Top,Bottom}Types.
  #14208

• Wasmtime now supports the use of environment variables to configure most CLI
  arguments in addition to the preexisting CLI flags.
  #14217

• Cranelift will now fold u{add,mul}_overflow results combined with brif
  instructions for more optimal codegen.
  #14217
  #14254

• Components can be tested for equality with a new Component::same API.
  #14257

• The Wasmtime C/C++ API now supports the component-model-implements feature.
  #14264

• Cranelift will now emit the {u,s}bfm instructions on AArch64.
  #14187

Changed

• The wide-arithmetic WebAssembly proposal is now enabled by default.
  #14110

• Config::operator_cost now applies to operators inside constant expressions
  (global initializers, element and data segment offsets, element segment
  expressions) and to the synthesized call to a module's start function.
  Previously each of those was charged 1 fuel unit regardless of the configured
  cost.
  #14215

• Wasmtime's WASI implementation will no longer over-read stdin where possible.
  #14077

• Wasmtime's WASIp2 implementation now maps host-level "broken pipe" errors to
  StreamError::Closed.
  #14107

• Wasmtime's WASIp2 implementation of wasi:http now validates ports in the
  same manner as wasip3.
  #14123

• Wasmtime's WASI implementation of wasi:filesystem now returns the
  is-directory error in some situations when a file is provided.
  #14135

• The wasmtime-wasi-http crate now has the p3 feature enabled by default.
  #14137

• Wasmtime's WASIp2 implementation of wasi:http now runs more hooks from the
  WasiHttpHooks trait in the same manner as wasip3.
  #14167

• Wasmtime now requires Rust 1.96.0 to compile.
  #14184

• Adjustments have been made to the scheduling of threads w.r.t. trapping
  behavior for cooperatively threaded components. These changes are made to
  align with the upstream component-model specification.
  #14146
  #14250

• Fuel for bulk operations is now consumed after the bulk operation has
  completed instead of up-front, restoring previous behavior where a failed very
  large memory growth doesn't trap the original program.
  #14213

• A number of future poll calls throughout the WASIp2 implementation now
  explicitly opt-out of Tokio's per-task cooperative budget to better uphold
  guarantees of WASIp2 APIs.
  #14265

• The run_concurrent function is now allowed to run recursively for separate
  stores, but it still can only be used at most once recursively for any one
  store.
  #14302

• The compile-time performance of the alias analysis in Cranelift has been
  greatly improved.
  #14306

48.0.2

Released 2026-09-10.

Changed

• Wasmtime's dependency on cap-primitives is now vendored within Wasmtime
  itself.
  #14225

Fixed

• Code generated by bindgen! is now compatible with the latest Rust nightly by
  default.
  #14307