CVE-2026-47261Wasmtime: WASI path_open(TRUNCATE) bypasses `FilePerms::WRITE` host restriction
- 7.5HighCVSS base score
- 0.36%Exploitation in 30 daysEPSS · top 70% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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.
Timeline
ID reserved
By GitHub_M
- 28 days later
· 28 days later
Published
- 1 day later
· 1 day later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N |
| NVDNVD · Analyzed | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N |
- EPSS (exploitation in 30 days)
- 0.36% · top 70% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.
Affected products
- affected >= 37.0.0, < 44.0.2
- affected >= 25.0.0, < 36.0.10
- affected < 24.0.9
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- crates.iowasmtime-wasiGHSA-2r75-cxrj-cmph (opens in a new tab)
References
References5
- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-2r75-cxrj-cmph (opens in a new tab)x_refsource_CONFIRM
- https://github.com/bytecodealliance/wasmtime/releases/tag/v24.0.9 (opens in a new tab)x_refsource_MISC
- https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.10 (opens in a new tab)x_refsource_MISC
- https://github.com/bytecodealliance/wasmtime/releases/tag/v44.0.2 (opens in a new tab)x_refsource_MISC
- https://github.com/bytecodealliance/wasmtime/releases/tag/v45.0.0 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-37001 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-2r75-cxrj-cmph (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-47261)Record last updated .