vulnerability / NVI-00017540 / Revision 1
wasmtime-wasi: WASI path_open(TRUNCATE) bypasses `FilePerms::WRITE` host restriction
GitHub lists this reviewed advisory for wasmtime-wasi, wasmtime-wasi, wasmtime-wasi. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
7.5 high
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
wasmtime-wasi
source listed>= 37.0.0, < 44.0.2
## 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: ```rust dir_descriptor.open_at( PathFlags::empty(), FILENAME, OpenFlags::TRUNCATE, DescriptorFlags::READ, ) ``` ```rust 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: ```rust if oflags.contains(OpenFlags::TRUNCATE) { opts.truncate(true).write(true); } ``` and the single line fix is: ```rust if oflags.cont
wasmtime-wasi
source listed>= 25.0.0, < 36.0.10
## 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: ```rust dir_descriptor.open_at( PathFlags::empty(), FILENAME, OpenFlags::TRUNCATE, DescriptorFlags::READ, ) ``` ```rust 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: ```rust if oflags.contains(OpenFlags::TRUNCATE) { opts.truncate(true).write(true); } ``` and the single line fix is: ```rust if oflags.cont
wasmtime-wasi
source listed< 24.0.9
## 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: ```rust dir_descriptor.open_at( PathFlags::empty(), FILENAME, OpenFlags::TRUNCATE, DescriptorFlags::READ, ) ``` ```rust 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: ```rust if oflags.contains(OpenFlags::TRUNCATE) { opts.truncate(true).write(true); } ``` and the single line fix is: ```rust if oflags.cont
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-2r75-cxrj-cmph ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.