# CVE-2026-27204: Wasmtime WASI implementations are vulnerable to guest-controlled resource exhaustion > A malicious WebAssembly guest can exhaust host resources in Wasmtime, causing denial of service; embedders must upgrade and configure limits. - **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Over the internet - **Victim action needed:** A user has to click or open something - **Fix available:** Yes - **Published:** 24 Feb 2026 - **Updated:** 27 Feb 2026 - **Also known as:** DEBIAN-CVE-2026-27204, GHSA-852m-cvvp-9p4w, JLSEC-2026-1352, RUSTSEC-2026-0020, UBUNTU-CVE-2026-27204 ## What is CVE-2026-27204? CVE-2026-27204 is a medium-severity denial of service vulnerability in bytecodealliance wasmtime, published on 24 Feb 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link. ### Official description Wasmtime is a runtime for WebAssembly. Prior to versions 24.0.6, 36.0.6, 4.0.04, 41.0.4, and 42.0.0, 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. Wasmtime 24.0.6, 36.0.6, 40.0.4, 41.0.4, and 42.0.0 have all been released with the fix for this issue. These versions do not prevent this issue in their default configuration to avoid breaking preexisting behaviors. All versions of Wasmtime have appropriate knobs to prevent this behavior, and Wasmtime 42.0.0-and-later will have these knobs tuned by default to prevent this issue from happening. There are no known workarounds for this issue without upgrading. Embedders are recommended to upgrade and configure their embeddings as necessary to prevent possibly-malicious guests from triggering this issue. Weakness: CWE-789 (Memory Allocation with Excessive Size Value), CWE-774 (Allocation of File Descriptors or Handles Without Limits or Throttling), CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-400 (Uncontrolled Resource Consumption) ## Which versions are affected by CVE-2026-27204? 7 open source packages ship an affected version, including wasmtime. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `wasmtime` | crates.io | All versions | 24.0.6 | | `wasmtime` | crates.io | All versions | 24.0.6 | | `wasmtime` | crates.io | From 0.0.0-0 | 24.0.6, 36.0.6, 40.0.4, 41.0.4 | | `wasmtime` | crates.io | From 25.0.0 | 36.0.6 | | `wasmtime` | crates.io | From 25.0.0 | 36.0.6 | | `wasmtime` | crates.io | From 37.0.0 | 40.0.4 | | `wasmtime` | crates.io | From 37.0.0 | 40.0.4 | Products: Bytecodealliance Wasmtime. ## How do I fix CVE-2026-27204? Upgrade wasmtime to a fixed version for your release line: 24.0.6, 36.0.6, 40.0.4 or 41.0.4. ## Is CVE-2026-27204 being exploited? There is no known exploitation of CVE-2026-27204 in the wild and no public exploit code. ## Other vulnerabilities in bytecodealliance wasmtime - [CVE-2026-34971](https://insights.sbomify.com/CVE-2026-34971/): Wasmtime miscompiled guest heap access enables sandbox escape on aarch64 Cranelift (critical 9.0) - [CVE-2026-34987](https://insights.sbomify.com/CVE-2026-34987/): Wasmtime with Winch compiler backend on aarch64 may allow a sandbox-escaping memory access (critical 9.0) - [CVE-2022-39393](https://insights.sbomify.com/CVE-2022-39393/): Wasmtime vulnerable to data leakage between instances in the pooling allocator (high 8.6) - [CVE-2022-24791](https://insights.sbomify.com/CVE-2022-24791/): Use after free in Wasmtime (high 8.1) - [CVE-2026-47261](https://insights.sbomify.com/CVE-2026-47261/): Wasmtime: WASI path_open(TRUNCATE) bypasses `FilePerms::WRITE` host restriction (high 7.5) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-27204 and fix it if it is affected. What it is: CVE-2026-27204 is a medium-severity denial of service vulnerability in bytecodealliance wasmtime, published on 24 Feb 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link. Exploitation: There is no known exploitation of CVE-2026-27204 in the wild and no public exploit code. Affected packages and fixed versions: - wasmtime (crates.io): affected all versions; fixed in 24.0.6 - wasmtime (crates.io): affected all versions; fixed in 24.0.6 - wasmtime (crates.io): affected from 0.0.0-0; fixed in 24.0.6, 36.0.6, 40.0.4, 41.0.4 - wasmtime (crates.io): affected from 25.0.0; fixed in 36.0.6 - wasmtime (crates.io): affected from 25.0.0; fixed in 36.0.6 - wasmtime (crates.io): affected from 37.0.0; fixed in 40.0.4 - wasmtime (crates.io): affected from 37.0.0; fixed in 40.0.4 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-27204/ (Markdown: https://insights.sbomify.com/CVE-2026-27204/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27204 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27204 - OSV: https://osv.dev/vulnerability/CVE-2026-27204 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-27204/ Summaries are generated and may contain mistakes; the official description above is the record.