Wasmtime segfault or unused out-of-sandbox load with `f64x2.splat` operator on x86-64
Priority LOW 19CWE-248Published · Updated
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- Active
- Attack complexity
- Low
- Attack requirements
- Present
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 2 without a fix
Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-248.
Summary
Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, On x86-64 platforms with SSE3 disabled Wasmtime's compilation of the f64x2.splat WebAssembly instruction with Cranelift may load 8 more bytes than is necessary. When signals-based-traps are disabled this can result in a uncaught segfault due to loading from unmapped guard pages. With guard pages disabled it's possible for out-of-sandbox data to be loaded, but this data is not visible to WebAssembly guests. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00236 14th percentileScored 2026-11-07
Fix Partial wasmtime (bytecodealliance): 24.0.7, 36.0.7, 42.0.2 +1wasmtime (crates.io): 24.0.7, 36.0.7, 42.0.2 +1Red Hat: 2 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
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 24.0.7; 25.0.0 to before 36.0.7; 37.0.0 to before 42.0.2; 43.0.0 to before 44.0.1 | 24.0.7, 36.0.7, 42.0.2, 44.0.1 | Patch available | CNA |
| — | wasmtime (crates.io) | before 24.0.7 | 24.0.7 | Patch available | GHSA-qqfj-4vcm-26hv |
| — | wasmtime (crates.io) | 25.0.0 to before 36.0.7 | 36.0.7 | Patch available | GHSA-qqfj-4vcm-26hv |
| — | wasmtime (crates.io) | 37.0.0 to before 42.0.2 | 42.0.2 | Patch available | GHSA-qqfj-4vcm-26hv |
| — | wasmtime (crates.io) | 43.0.0 to before 43.0.1 | 43.0.1 | Patch available | GHSA-qqfj-4vcm-26hv |
- wasmtime Vendorbytecodealliance Affected before 24.0.7; 25.0.0 to before 36.0.7; 37.0.0 to before 42.0.2; 43.0.0 to before 44.0.1 Fixed in 24.0.7, 36.0.7, 42.0.2, 44.0.1 Patch available CNA
- wasmtime (crates.io) Vendor— Affected before 24.0.7 Fixed in 24.0.7 Patch available GHSA-qqfj-4vcm-26hv
- wasmtime (crates.io) Vendor— Affected 25.0.0 to before 36.0.7 Fixed in 36.0.7 Patch available GHSA-qqfj-4vcm-26hv
- wasmtime (crates.io) Vendor— Affected 37.0.0 to before 42.0.2 Fixed in 42.0.2 Patch available GHSA-qqfj-4vcm-26hv
- wasmtime (crates.io) Vendor— Affected 43.0.0 to before 43.0.1 Fixed in 43.0.1 Patch available GHSA-qqfj-4vcm-26hv
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* | before 24.0.7; 25.0.0 to before 36.0.7; 37.0.0 to before 42.0.2; 43.0.0 to before 43.0.1 | Vulnerable | bytecodealliance |
- cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* Versions before 24.0.7; 25.0.0 to before 36.0.7; 37.0.0 to before 42.0.2; 43.0.0 to before 43.0.1 Vulnerable ·bytecodealliance
Remediation
- Fix · CNA wasmtime (bytecodealliance) Fixed in 24.0.7, 36.0.7, 42.0.2, 44.0.1
- Fix · GHSA-qqfj-4vcm-26hv wasmtime (crates.io) Fixed in 24.0.7 Advisory →
- Fix · GHSA-qqfj-4vcm-26hv wasmtime (crates.io) Fixed in 36.0.7 Advisory →
- Fix · GHSA-qqfj-4vcm-26hv wasmtime (crates.io) Fixed in 42.0.2 Advisory →
- Fix · GHSA-qqfj-4vcm-26hv wasmtime (crates.io) Fixed in 43.0.1 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Connectivity Link 1 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-34944
- 2026-10-03 Alias added: GHSA-qqfj-4vcm-26hv
References
More bytecodealliance Wasmtime vulnerabilities
- TI-2026-21632 Wasmtime is vulnerable to panic when dropping a `[Typed]Func::call_async` future CVSS 4.0MEDIUM 6.9
- TI-2023-11636 Guest-controlled out-of-bounds read/write on x86_64 in wasmtime CVSS 3.1CRITICAL 10.0
- TI-2022-18765 Wasmtime vulnerable to data leakage between instances in the pooling allocator CVSS 3.1HIGH 8.6
- TI-2022-08604 Use after free in Wasmtime CVSS 3.1CRITICAL 9.8
- TI-2022-18766 wasmtime_trap_code C API function has out of bounds write vulnerability CVSS 3.1CRITICAL 9.8
- TI-2026-27209 Wasmtime with Winch compiler backend on aarch64 may allow a sandbox-escaping memory access CVSS 4.0CRITICAL 9.0
Sources
- CVE-2026-34944 · CVE Program
- CVE-2026-34944 · NVD
- FIRST EPSS
- GHSA-qqfj-4vcm-26hv · GitHub Advisory Database · CC BY 4.0
- CVE-2026-34944 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences