Wasmtime WASI implementations are vulnerable to guest-controlled resource exhaustion

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

5.9 · CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L · score source

EPSS

• CVE-2026-27204: 0.40% estimated exploitation activity in the next 30 days; percentile 34.66 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Wasmtime's implementation of WASI host interfaces are susceptible to guest-controlled resource exhaustion on the host. Wasmtime did not appropriately place limits on resource allocations requested by the guests. This serves as a Denial of Service vector where a guest can induce a range of crashing behaviors on the host such as: Allocating arbitrarily large amounts of host memory. Causing an allocation failure on the host, which in Rust defaults to aborting the process. Causing a panic on the host due to over-large allocations being performed. Cause degredation in performance of the host by holding excessive host memory alive. Wasmtime's security bug policy considers all of these behaviors a security vulnerability. Wasmtime's implementation of WASI has a number of different ways that resource exhaustion could happen, and fixing any one of them is insufficient from solving this vulnerability. A number of individual issues are grouped within this advisory and as a whole represent…

Published by the source

24 Feb 2026, 20:47 UTC

Last modified by the source

27 Feb 2026, 20:25 UTC

Source last checked

26 Oct 2026, 15:42 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-852m-cvvp-9p4w

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# Patch Next advisory brief: CVE-2026-27204

Advisory: Wasmtime WASI implementations are vulnerable to guest-controlled resource exhaustion
IDs: CVE-2026-27204, GHSA-852m-cvvp-9p4w
Record: https://patchnext.com/advisories/cve-2026-27204 (revision 1, source checked 26 Oct 2026, 15:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: wasmtime 40.0.4, 36.0.6, 24.0.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io wasmtime: affected < 24.0.6; >= 25.0.0, < 36.0.6; >= 37.0.0, < 40.0.4; fixed in 24.0.6, 40.0.4, 36.0.6

## Suggested inspection (read-only)
- crates.io wasmtime: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on wasmtime.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-852m-cvvp-9p4w (GitHub-reviewed advisory GHSA-852m-cvvp-9p4w lists affected ranges: crates.io wasmtime >=0 =25.0.0 =37.0.0 <40.0.4)

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