Vulnerability in wasmtime-wasi (CVE-2026-47261)
Summary
Vulnerability in wasmtime-wasi (CVE-2026-47261). Data can be tampered with by attackers. Exploitable via path_open. Mitigation: upgrade to 24.0.9 or later.
Original description
The description as published by the source.
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.
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-47261 has been found in wasmtime-wasi.
Attackers can target a specific entry point like path_open over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 7.5/10.
What to do: upgrade wasmtime-wasi to 24.0.9 or later.
If unsure, ask your IT team or search "wasmtime-wasi CVE-2026-47261" on the vendor's site.
CVE-2026-47261 (wasmtime-wasi) — CWE-284 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: path_open / FilePerms / ERRNO_PERM / WasiCtxBuilder
Patched: 24.0.9 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-284) exists in wasmtime-wasi. Attackers reach the vulnerable code path via path_open without authentication.
Check the vendor advisory for the affected versions of wasmtime-wasi. Attack surface: path_open / FilePerms / ERRNO_PERM / WasiCtxBuilder.
Severity: High (CVSS 7.5/10). Data can be tampered with by attackers.
Update to 24.0.9.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'wasmtime-wasi' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'wasmtime-wasi' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
wasmtime-wasiを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade wasmtime-wasi to 24.0.9ステージング環境で 24.0.9 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-47261 rust-wasmtime
- Ubuntu UBUNTU-CVE-2026-47261 rust-wasmtime
References
- advisory rustsec.org
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package crates.io
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com