# CVE-2026-35195: Wasmtime has an out-of-bounds write or crash when transcoding component model strings > A guest component can trigger an out-of-bounds write in Wasmtime, potentially causing host crashes or arbitrary memory corruption. - **Severity:** Medium 6.1 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 9 Apr 2026 - **Updated:** 13 Apr 2026 - **Also known as:** DEBIAN-CVE-2026-35195, GHSA-394w-hwhg-8vgm, JLSEC-2026-1364, RUSTSEC-2026-0091, UBUNTU-CVE-2026-35195 ## What is CVE-2026-35195? CVE-2026-35195 is a medium-severity memory corruption vulnerability in bytecodealliance wasmtime, published on 9 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim. ### Official description Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime's implementation of transcoding strings between components contains a bug where the return value of a guest component's realloc is not validated before the host attempts to write through the pointer. This enables a guest to cause the host to write arbitrary transcoded string bytes to an arbitrary location up to 4GiB away from the base of linear memory. These writes on the host could hit unmapped memory or could corrupt host data structures depending on Wasmtime's configuration. Wasmtime by default reserves 4GiB of virtual memory for a guest's linear memory meaning that this bug will by default on hosts cause the host to hit unmapped memory and abort the process due to an unhandled fault. Wasmtime can be configured, however, to reserve less memory for a guest and to remove all guard pages, so some configurations of Wasmtime may lead to corruption of data outside of a guest's linear memory, such as host data structures or other guests's linear memories. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1. Weakness: CWE-787 (Out-of-bounds Write) ## Which versions are affected by CVE-2026-35195? 9 open source packages ship an affected version, including wasmtime. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `wasmtime` | crates.io | All versions | 24.0.7 | | `wasmtime` | crates.io | All versions | 24.0.7 | | `wasmtime` | crates.io | From 0.0.0-0 | 24.0.7, 36.0.7, 42.0.2, 43.0.1 | | `wasmtime` | crates.io | From 25.0.0 | 36.0.7 | | `wasmtime` | crates.io | From 25.0.0 | 36.0.7 | | `wasmtime` | crates.io | From 37.0.0 | 42.0.2 | | `wasmtime` | crates.io | From 37.0.0 | 42.0.2 | | `wasmtime` | crates.io | From 43.0.0 | 43.0.1 | | `wasmtime` | crates.io | From 43.0.0 | 43.0.1 | Products: Bytecodealliance Wasmtime. ## How do I fix CVE-2026-35195? Upgrade wasmtime to a fixed version for your release line: 24.0.7, 36.0.7, 42.0.2 or 43.0.1. ## Is CVE-2026-35195 being exploited? There is no known exploitation of CVE-2026-35195 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-2026-35195 and fix it if it is affected. What it is: CVE-2026-35195 is a medium-severity memory corruption vulnerability in bytecodealliance wasmtime, published on 9 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-35195 in the wild and no public exploit code. Affected packages and fixed versions: - wasmtime (crates.io): affected all versions; fixed in 24.0.7 - wasmtime (crates.io): affected all versions; fixed in 24.0.7 - wasmtime (crates.io): affected from 0.0.0-0; fixed in 24.0.7, 36.0.7, 42.0.2, 43.0.1 - wasmtime (crates.io): affected from 25.0.0; fixed in 36.0.7 - wasmtime (crates.io): affected from 25.0.0; fixed in 36.0.7 - wasmtime (crates.io): affected from 37.0.0; fixed in 42.0.2 - wasmtime (crates.io): affected from 37.0.0; fixed in 42.0.2 - wasmtime (crates.io): affected from 43.0.0; fixed in 43.0.1 - wasmtime (crates.io): affected from 43.0.0; fixed in 43.0.1 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-2026-35195/ (Markdown: https://insights.sbomify.com/CVE-2026-35195/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-35195 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-35195 - OSV: https://osv.dev/vulnerability/CVE-2026-35195 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-35195/ Summaries are generated and may contain mistakes; the official description above is the record.