Wasmtime vulnerable to out of bounds read/write with zero-memory-pages configuration

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Wasmtime is a standalone runtime for WebAssembly. Prior to version 2.0.2, there is a bug in Wasmtime's implementation of its pooling instance allocator when the allocator is configured to give WebAssembly instances a maximum of zero pages of memory. In this configuration, the virtual memory mapping for WebAssembly memories did not meet the compiler-required configuration requirements for safely executing WebAssembly modules. Wasmtime's default settings require virtual memory page faults to indicate that wasm reads/writes are out-of-bounds, but the pooling allocator's configuration would not create an appropriate virtual memory mapping for this meaning out of bounds reads/writes can successfully read/write memory unrelated to the wasm sandbox within range of the base address of the memory mapping created by the pooling allocator. This bug is not applicable with the default settings of the `wasmtime` crate. This bug can only be triggered by setting `InstanceLimits::memory_pages` to zero. This is expected to be a very rare configuration since this means that wasm modules cannot allocate any pages of linear memory. All wasm modules produced by all current toolchains are highly likely to use linear memory, so it's expected to be unlikely that this configuration is set to zero by any production embedding of Wasmtime. This bug has been patched and users should upgrade to Wasmtime 2.0.2. This bug can be worked around by increasing the `memory_pages` allotment when configuring the pooling allocator to a value greater than zero. If an embedding wishes to still prevent memory from actually being used then the `Store::limiter` method can be used to dynamically disallow growth of memory beyond 0 bytes large. Note that the default `memory_pages` value is greater than zero.

Source published

10 Nov 2022 00:00:00 UTC

Source modified

23 Apr 2025 16:39:17 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 5.9 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N

Wasmtime is a standalone runtime for WebAssembly. Prior to version 2.0.2, there is a bug in Wasmtime's implementation of its pooling instance allocator when the allocator is configured to give WebAssembly instances a maximum of zero pages of memory. In this configuration, the virtual memory mapping for WebAssembly memories did not meet the compiler-required configuration requirements for safely executing WebAssembly modules. Wasmtime's default settings require virtual memory page faults to indicate that wasm reads/writes are out-of-bounds, but the pooling allocator's configuration would not create an appropriate virtual memory mapping for this meaning out of bounds reads/writes can successfully read/write memory unrelated to the wasm sandbox within range of the base address of the memory mapping created by the pooling allocator. This bug is not applicable with the default settings of the `wasmtime` crate. This bug can only be triggered by setting `InstanceLimits::memory_pages` to zero. This is expected to be a very rare configuration since this means that wasm modules cannot allocate any pages of linear memory. All wasm modules produced by all current toolchains are highly likely to use linear memory, so it's expected to be unlikely that this configuration is set to zero by any production embedding of Wasmtime. This bug has been patched and users should upgrade to Wasmtime 2.0.2. This bug can be worked around by increasing the `memory_pages` allotment when configuring the pooling allocator to a value greater than zero. If an embedding wishes to still prevent memory from actually being used then the `Store::limiter` method can be used to dynamically disallow growth of memory beyond 0 bytes large. Note that the default `memory_pages` value is greater than zero.

Source published

Nov 10, 2022, 12:00:00 AM (timezone not stated)

Source modified

Apr 23, 2025, 4:39:17 PM (timezone not stated)

Observed here

10 Nov 2026 00:16:07 UTC

Source terms

ENISA EUVD · source terms and attribution apply

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 5.9 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N

Wasmtime is a standalone runtime for WebAssembly. Prior to version 2.0.2, there is a bug in Wasmtime's implementation of its pooling instance allocator when the allocator is configured to give WebAssembly instances a maximum of zero pages of memory. In this configuration, the virtual memory mapping for WebAssembly memories did not meet the compiler-required configuration requirements for safely executing WebAssembly modules. Wasmtime's default settings require virtual memory page faults to indicate that wasm reads/writes are out-of-bounds, but the pooling allocator's configuration would not create an appropriate virtual memory mapping for this meaning out of bounds reads/writes can successfully read/write memory unrelated to the wasm sandbox within range of the base address of the memory mapping created by the pooling allocator. This bug is not applicable with the default settings of the `wasmtime` crate. This bug can only be triggered by setting `InstanceLimits::memory_pages` to zero. This is expected to be a very rare configuration since this means that wasm modules cannot allocate any pages of linear memory. All wasm modules produced by all current toolchains are highly likely to use linear memory, so it's expected to be unlikely that this configuration is set to zero by any production embedding of Wasmtime. This bug has been patched and users should upgrade to Wasmtime 2.0.2. This bug can be worked around by increasing the `memory_pages` allotment when configuring the pooling allocator to a value greater than zero. If an embedding wishes to still prevent memory from actually being used then the `Store::limiter` method can be used to dynamically disallow growth of memory beyond 0 bytes large. Note that the default `memory_pages` value is greater than zero.

Source published

10 Nov 2022 20:15:11 UTC

Source modified

17 Jun 2026 04:58:16 UTC

Observed here

24 Oct 2026 21:17:10 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 5.9 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N

CVSS 3.1 · [email protected] · Primary · 7.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

### Impact There is a bug in Wasmtime's implementation of its pooling instance allocator when the allocator is configured to give WebAssembly instances a maximum of zero pages of memory. In this configuration the virtual memory mapping for WebAssembly memories did not meet the compiler-required configuration requirements for safely executing WebAssembly modules. Wasmtime's default settings require virtual memory page faults to indicate that wasm reads/writes are out-of-bounds, but the pooling allocator's configuration would not create an appropriate virtual memory mapping for this meaning out of bounds reads/writes can successfully read/write memory unrelated to the wasm sandbox within range of the base address of the memory mapping created by the pooling allocator. This bug can only be triggered by setting [`InstanceLimits::memory_pages`](https://docs.rs/wasmtime/2.0.1/wasmtime/struct.InstanceLimits.html#structfield.memory_pages) to zero. This is expected to be a very rare configuration since this means that wasm modules cannot allocate any pages of linear memory. All wasm modules produced by all current toolchains are highly likely to use linear memory, so it's expected to be unlikely that this configuration is set to zero by any production embedding of Wasmtime, hence the low severity of this bug despite the critical consequences. ### Patches This bug has been patched and users should upgrade to Wasmtime 2.0.2. ### Workarounds One way to mitigate this issue is to disable usage of the pooling allocator. Note that the pooling allocator is not enabled by default. This bug can also only be worked around by increasing the `memory_pages` allotment when configuring the pooling allocator to a value greater than zero. If an embedding wishes to still prevent memory from actually being used then the `Store::limiter` method can be used to dynamically disallow growth of memory beyond 0 bytes large. Note that the default `memory_pages` value is greater than zero. This bug is not applicable with the default settings of the `wasmtime` crate. ### References * [`Config::allocation_strategy`](https://docs.rs/wasmtime/2.0.1/wasmtime/struct.Config.html#method.allocation_strategy) - configuration required to enable the pooling allocator. * [`InstanceLimits::memory_pages`](https://docs.rs/wasmtime/2.0.1/wasmtime/struct.InstanceLimits.html#structfield.memory_pages) - configuration field that, when zero, exhibits this bug. * [`Store::limiter`](https://docs.rs/wasmtime/2.0.1/wasmtime/struct.Store.html#method.limiter) - means of limiting memory without using `memory_pages` * [Mailing list announcement](https://groups.google.com/a/bytecodealliance.org/g/sec-announce/c/c1HBDDJwNPA) * [Patch for the `release-2.0.0` branch](https://github.com/bytecodealliance/wasmtime/commit/e60c3742904ccbb3e26da201c9221c38a4981d72) ### For more information If you have any questions or comments about this advisory: * Reach out to us on [the Bytecode Alliance Zulip chat](https://bytecodealliance.zulipchat.com/#narrow/stream/217126-wasmtime) * Open an issue in [the bytecodealliance/wasmtime repository](https://github.com/bytecodealliance/wasmtime/)

Source published

10 Nov 2022 21:09:02 UTC

Source modified

2 May 2025 12:49:46 UTC

Observed here

24 Oct 2026 13:19:54 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N

Publisher rating · MODERATE

Bug in Wasmtime's implementation of its pooling instance allocator when the allocator is configured to give WebAssembly instances a maximum of zero pages of memory. In this configuration, the virtual memory mapping for WebAssembly memories did not meet the compiler-required configuration requirements for safely executing WebAssembly modules. Wasmtime's default settings require virtual memory page faults to indicate that wasm reads/writes are out-of-bounds, but the pooling allocator's configuration would not create an appropriate virtual memory mapping for this meaning out of bounds reads/writes can successfully read/write memory unrelated to the wasm sandbox within range of the base address of the memory mapping created by the pooling allocator. This bug is not applicable with the default settings of the `wasmtime` crate. This bug can only be triggered by setting `InstanceLimits::memory_pages` to zero. This is expected to be a very rare configuration since this means that wasm modules cannot allocate any pages of linear memory. All wasm modules produced by all current toolchains are highly likely to use linear memory, so it's expected to be unlikely that this configuration is set to zero by any production embedding of Wasmtime.

Source published

10 Nov 2022 12:00:00 UTC

Source modified

12 Oct 2026 18:00:04 UTC

Observed here

24 Oct 2026 13:19:54 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

This is an entry in the RustSec database for the Wasmtime security advisory located at https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-44mr-8vmm-wjhg. For more information see the GitHub-hosted security advisory.

Source published

5 Nov 2022 12:00:00 UTC

Source modified

12 Oct 2026 18:00:05 UTC

Observed here

24 Oct 2026 13:19:54 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N