Symlink following in Wasmtime lets guests escape sandbox via rename
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- Passive
- Attack complexity
- Low
- Attack requirements
- Present
- Impact type
- —
- Confidentiality · integrity · availability
- High · High · Low
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA.
Summary
Wasmtime versions before 36.0.18, from 37.0.0 before 48.0.6, and from 49.0.0 before 49.0.3 are affected. The wasmtime-wasi component re-appends a trailing slash to rename source paths, so renameat on macOS and FreeBSD hosts follows directory symlinks (CWE-61). A guest with sandbox write access can rename a relative symlink to move host directories into its sandbox and read or write them.
Written with Claude Haiku 5.5 from the sources below · 2026-11-04
Description from the CNA
wasmtime-wasi in Wasmtime before 36.0.18, 37.0.0 before 48.0.6, and 49.0.0 before 49.0.3 re-appends a trailing slash to rename source paths, causing renameat on macOS and FreeBSD hosts to follow directory symlinks. A guest with sandbox write access can rename a relative symlink such as "up/" to move host directories into its sandbox and read or write them.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| bytecodealliance | wasmtime | before 36.0.18; 37.0.0 to before 48.0.6; 49.0.0 to before 49.0.3 | 36.0.18, 48.0.6, 49.0.3 | Patch available | CNA |
- wasmtime Vendorbytecodealliance Affected before 36.0.18; 37.0.0 to before 48.0.6; 49.0.0 to before 49.0.3 Fixed in 36.0.18, 48.0.6, 49.0.3 Patch available CNA
CPE names Threatist (inferred) · 1
Inferred from how NVD named this product before; not given by a source.
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:*:*:* | — | — | bytecodealliance |
- cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:*:*:* Versions — — ·bytecodealliance
Remediation
Fixed versions for Wasmtime are 36.0.18, 48.0.6 and 49.0.3. Upgrade to the fixed version on your release line.
Written with Claude Haiku 5.5 from the sources below · 2026-11-04
- Fix · CNA wasmtime (bytecodealliance) Fixed in 36.0.18, 48.0.6, 49.0.3
Timeline
- 2026-10-28 Threatist record created from CVE-2026-118688
- 2026-10-28 Alias added: GHSA-63fr-xrxj-8wrx
- 2026-10-30 Priority changed: MEDIUM → LOW
- 2026-11-04 CISA SSVC decision points changed
- 2026-11-04 Priority changed: LOW → MEDIUM
References
More bytecodealliance vulnerabilities
- TI-2026-85541 WAMR fast interpreter loader heap overflow via constant deduplication mismatch CVSS 4.0HIGH 8.8
- TI-2024-16741 An issue in bytecodealliance wasm-micro-runtime before v.b3f728c and fixed in commit… CVSS 3.1HIGH 8.8
- TI-2024-22658 An out-of-bound memory read vulnerability was discovered in Bytecode Alliance… CVSS 3.1HIGH 7.5
- TI-2024-18300 wasm-micro-runtime (aka WebAssembly Micro Runtime or WAMR) 06df58f is vulnerable to NULL… CVSS 3.1HIGH 7.5
- TI-2023-26034 An heap overflow vulnerability was discovered in Bytecode alliance wasm-micro-runtime… CVSS 3.1HIGH 7.5
- TI-2025-33969 WebAssembly Micro Runtime's `--addr-pool` option allows all IPv4 addresses when subnet mask is not specified CVSS 4.0MEDIUM 6.9
Sources
- CVE-2026-118688 · CVE Program
- CVE-2026-118688 · NVD
- FIRST EPSS
- GHSA-63fr-xrxj-8wrx · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences