CVE-2026-47261

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data tampering.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-06-15 21:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-25 23:10 UTC Last updatedMost recent change to the record

Details

Published

2026-06-15 21:17 UTC

Last modified

2026-10-25 23:10 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-284 · Improper access control

Record status

Analyzed

Affected

• Bytecodealliance Wasmtime < 24.0.9
• Bytecodealliance Wasmtime < 36.0.10
• Bytecodealliance Wasmtime < 44.0.2

Attack profile CVSS 3.1 · 7.5

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

High

Availability

None