Vulnerability-Lookup

CVE-2026-27195 (GCVE-0-2026-27195)

Vulnerability from cvelistv5 – Published: 2026-02-24 21:15 – Updated: 2026-02-24 21:36

Title

Wasmtime is vulnerable to panic when dropping a `[Typed]Func::call_async` future

Summary

Wasmtime is a runtime for WebAssembly. 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.

Severity ?

6.9 (Medium)


                        
                          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

CWE

CWE-755 - Improper Handling of Exceptional Conditions

Assigner

GitHub_M

References

URL

Tags

	https://github.com/bytecodealliance/wasmtime/secu…	x_refsource_CONFIRM
	https://github.com/bytecodealliance/wasmtime/comm…	x_refsource_MISC
	https://github.com/bytecodealliance/wasmtime/comm…	x_refsource_MISC
	https://bytecodealliance.zulipchat.com/#narrow/ch…	x_refsource_MISC
	https://github.com/bytecodealliance/wasmtime/rele…	x_refsource_MISC
	https://github.com/bytecodealliance/wasmtime/rele…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	bytecodealliance	wasmtime	Affected: >= 39.0.0, < 40.0.4 Affected: >= 41.0.0, < 41.0.4

Show details on NVD website

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cve-2026-27195

Vulnerability from osv_rustsec

Published

2026-02-24 12:00

Modified

2026-02-24 19:42

Summary

Panic when dropping a `[Typed]Func::call_async` future

Details

This is an entry in the RustSec database for the Wasmtime security advisory located at https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xjhv-v822-pf94 For more information see the GitHub-hosted security advisory.

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "categories": [],
        "cvss": "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",
        "informational": null
      },
      "ecosystem_specific": {
        "affected_functions": null,
        "affects": {
          "arch": [],
          "functions": [],
          "os": []
        }
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "wasmtime",
        "purl": "pkg:cargo/wasmtime"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "39.0.0"
            },
            {
              "fixed": "40.0.4"
            },
            {
              "introduced": "41.0.0"
            },
            {
              "fixed": "41.0.4"
            }
          ],
          "type": "SEMVER"
        }
      ],
      "versions": []
    }
  ],
  "aliases": [
    "CVE-2026-27195",
    "GHSA-xjhv-v822-pf94"
  ],
  "database_specific": {
    "license": "CC0-1.0"
  },
  "details": "This is an entry in the RustSec database for the Wasmtime security advisory\nlocated at\nhttps://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xjhv-v822-pf94\nFor more information see the GitHub-hosted security advisory.",
  "id": "RUSTSEC-2026-0022",
  "modified": "2026-02-24T19:42:18Z",
  "published": "2026-02-24T12:00:00Z",
  "references": [
    {
      "type": "PACKAGE",
      "url": "https://crates.io/crates/wasmtime"
    },
    {
      "type": "ADVISORY",
      "url": "https://rustsec.org/advisories/RUSTSEC-2026-0022.html"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xjhv-v822-pf94"
    }
  ],
  "related": [],
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Panic when dropping a `[Typed]Func::call_async` future"
}

GHSA-XJHV-V822-PF94

Vulnerability from github – Published: 2026-02-24 20:44 – Updated: 2026-02-24 20:44

Summary

Wasmtime is vulnerable to panic when dropping a `[Typed]Func::call_async` future

Details

The affected versions of Wasmtime can panic if the host embedder drops the future returned by wasmtime::component::[Typed]Func::call_async before it resolves.

Details

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:

The host embedding calls [Typed]Func::call_async on a function exported by a component, polling the returned Future once.
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.
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.
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.
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.

Impact

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.

Patches

Wasmtime 40.0.4 and 41.0.4 have been patched to fix this issue. Versions 42.0.0 and later are not affected.

Workarounds

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.

Resources

This was first reported in https://bytecodealliance.zulipchat.com/#narrow/channel/206238-general/topic/Panic.20in.20Wasmtime.2041.2E0.2E3.20.28runtime.2Fconcurrent.2Fcomponent.29

Severity ?

6.9 (Medium)


                  
                    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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "wasmtime"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "39.0.0"
            },
            {
              "fixed": "40.0.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "wasmtime"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "41.0.0"
            },
            {
              "fixed": "41.0.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-27195"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-755"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-24T20:44:46Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "The affected versions of Wasmtime can panic if the host embedder drops the future returned by `wasmtime::component::[Typed]Func::call_async` before it resolves.\n\n### Details\n\nStarting 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:\n\n1. The host embedding calls `[Typed]Func::call_async` on a function exported by a component, polling the returned `Future` once.\n2. 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.\n3. 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.\n4. 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.\n5. 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.\n\n### Impact\nWhen 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.\n\n### Patches\nWasmtime 40.0.4 and 41.0.4 have been patched to fix this issue. Versions 42.0.0 and later are not affected.\n\n### Workarounds\nIf 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.\n\n### Resources\nThis was first reported in https://bytecodealliance.zulipchat.com/#narrow/channel/206238-general/topic/Panic.20in.20Wasmtime.2041.2E0.2E3.20.28runtime.2Fconcurrent.2Fcomponent.29",
  "id": "GHSA-xjhv-v822-pf94",
  "modified": "2026-02-24T20:44:46Z",
  "published": "2026-02-24T20:44:46Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xjhv-v822-pf94"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/commit/9e51c0d9a240a9613d279c061f82286bd11383fd"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/commit/d86b00736b9ece60b3c81e52f7a7e4cdd9f7d895"
    },
    {
      "type": "WEB",
      "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"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/bytecodealliance/wasmtime"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/releases/tag/v40.0.4"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/releases/tag/v41.0.4"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Wasmtime is vulnerable to panic when dropping a `[Typed]Func::call_async` future"
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-27195 (GCVE-0-2026-27195)

cve-2026-27195

Vulnerability from osv_rustsec

GHSA-XJHV-V822-PF94

Details

Impact

Patches

Workarounds

Resources

Tags

Sightings

Nomenclature