GHSA-2r75-cxrj-cmph

Опубликовано: 05 июн. 2026

Источник: github

Github: Прошло ревью

CVSS3: 7.5

Описание

wasmtime-wasi: WASI path_open(TRUNCATE) bypasses FilePerms::WRITE host restriction

Summary

In wasmtime-wasi, when a filesystem preopen is given DirPerms::all() and FilePerms::READ without FilePerms::WRITE, this wasmtime-wasi enforced access control mechanism can be bypassed by using the wasip2 descriptor.open-at or wasip1 path_open interfaces by opening a file with OpenFlags::TRUNCATE oflag only, for example:

dir_descriptor.open_at( PathFlags::empty(), FILENAME, OpenFlags::TRUNCATE, DescriptorFlags::READ, )

wasip1::path_open( dir_fd, 0, FILENAME, wasip1::OFLAGS_TRUNC, wasip1::RIGHTS_FD_READ, 0, 0 )

The root cause is that the clause that considered OpenFlags::TRUNCATE did not set open_mode |= OpenMode::WRITE;, used later in that function for the access control check against FilePerms for whether opening that file is permitted. With the bug corrected, these calls to open-at and path_open fail with error-code.not-permitted and ERRNO_PERM respectively.

The bug in crates/wasi/src/filesystem.rs, Dir::open_at, lines 967–969:

if oflags.contains(OpenFlags::TRUNCATE) { opts.truncate(true).write(true); }

and the single line fix is:

if oflags.contains(OpenFlags::TRUNCATE) { opts.truncate(true).write(true); open_mode |= OpenMode::WRITE; }

Only wasmtime-wasi embeddings that use a combination of DirPerms::MUTATE with FilePerms::READ are affected by this bug, e.g. those that use in the WasiCtxBuilder:

builder.preopened_dir("readonly", "readonly", DirPerms::READ | DirPerms::MUTATE, FilePerms::READ);

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.

Ссылки

Пакеты

Наименование

wasmtime-wasi

rust

Затронутые версииВерсия исправления

>= 37.0.0, < 44.0.2

44.0.2

Наименование

wasmtime-wasi

rust

Затронутые версииВерсия исправления

>= 25.0.0, < 36.0.10

36.0.10

Наименование

wasmtime-wasi

rust

Затронутые версииВерсия исправления

< 24.0.9

24.0.9

EPSS

Процентиль: 28%

0.00357

Низкий

7.5 High

CVSS3

CVE ID

CVE-2026-47261

Дефекты

CWE-284

Связанные уязвимости

CVE-2026-47261

CVSS3: 7.5

ubuntu

около 2 месяцев назад

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...