# CVE-2026-47261: rust-wasmtime: Wasmtime is a runtime for WebAssembly

CVE-2026-47261 is fixed in rust-wasmtime on 1 platform by DEBIAN-CVE-2026-47261 (version 36.0.11+dfsg-1), released June 24, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-47261
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0036
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 15, 2026

## Description

Wasmtime is a runtime for WebAssembly. In versions prior to 24.0.9, 36.0.10, and 44.0.2, when a filesystem preopen is given DirPerms::all() and FilePerms::READ without FilePerms::WRITE, this access control mechanism can be bypassed via the wasip2 descriptor.open-at or wasip1 path_open interfaces by opening a file with only the OpenFlags::TRUNCATE oflag. The root cause is that the clause handling OpenFlags::TRUNCATE in crates/wasi/src/filesystem.rs (Dir::open_at, lines 967–969) did not set open_mode |= OpenMode::WRITE;, which is later used for the access control check against FilePerms to determine whether opening the file is permitted; the single-line fix adds that missing assignment, after which the affected calls correctly fail with error-code.not-permitted and ERRNO_PERM respectively. Only wasmtime-wasi embeddings that combine DirPerms::MUTATE with FilePerms::READ are affected by this bug. In particular, the Wasmtime project's wasmtime-cli's use of wasmtime-wasi is not affected, because it always sets FilePerms::all() for all preopens. This issue has been fixed in versions 24.0.9, 36.0.10 and44.0.2.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | rust-wasmtime Debian 14 | 36.0.11+dfsg-1 | [DEBIAN-CVE-2026-47261](https://patchblox.com/security/data/fix/linux/debian-cve-2026-47261.md) | Jun 24, 2026 |

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