Wasmtime WASI implementations are vulnerable to guest-controlled resource exhaustion
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- Passive
- Attack complexity
- Low
- Attack requirements
- Present
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 1 without a fix
Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-400.
Summary
Wasmtime is a runtime for WebAssembly. Prior to versions 24.0.6, 36.0.6, 4.0.04, 41.0.4, and 42.0.0, Wasmtime's implementation of WASI host interfaces are susceptible to guest-controlled resource exhaustion on the host. Wasmtime did not appropriately place limits on resource allocations requested by the guests. This serves as a Denial of Service vector. Wasmtime 24.0.6, 36.0.6, 40.0.4, 41.0.4, and 42.0.0 have all been released with the fix for this issue. These versions do not prevent this issue in their default configuration to avoid breaking preexisting behaviors. All versions of Wasmtime have appropriate knobs to prevent this behavior, and Wasmtime 42.0.0-and-later will have these knobs tuned by default to prevent this issue from happening. There are no known workarounds for this issue without upgrading. Embedders are recommended to upgrade and configure their embeddings as necessary to prevent possibly-malicious guests from triggering this issue.
Why it matters now
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 24.0.6; 25.0.0 to before 36.0.6; 37.0.0 to before 40.0.4; 41.0.0 to before 41.0.4 | 24.0.6, 36.0.6, 40.0.4, 41.0.4 | Patch available | CNA |
| — | wasmtime (crates.io) | before 24.0.6 | 24.0.6 | Patch available | GHSA-852m-cvvp-9p4w |
| — | wasmtime (crates.io) | 25.0.0 to before 36.0.6 | 36.0.6 | Patch available | GHSA-852m-cvvp-9p4w |
| — | wasmtime (crates.io) | 37.0.0 to before 40.0.4 | 40.0.4 | Patch available | GHSA-852m-cvvp-9p4w |
- wasmtime Vendorbytecodealliance Affected before 24.0.6; 25.0.0 to before 36.0.6; 37.0.0 to before 40.0.4; 41.0.0 to before 41.0.4 Fixed in 24.0.6, 36.0.6, 40.0.4, 41.0.4 Patch available CNA
- wasmtime (crates.io) Vendor— Affected before 24.0.6 Fixed in 24.0.6 Patch available GHSA-852m-cvvp-9p4w
- wasmtime (crates.io) Vendor— Affected 25.0.0 to before 36.0.6 Fixed in 36.0.6 Patch available GHSA-852m-cvvp-9p4w
- wasmtime (crates.io) Vendor— Affected 37.0.0 to before 40.0.4 Fixed in 40.0.4 Patch available GHSA-852m-cvvp-9p4w
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* | before 24.0.6; 25.0.0 to before 36.0.6; 37.0.0 to before 40.0.4; 41.0.0 to before 41.0.4 | Vulnerable | bytecodealliance |
- cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* Versions before 24.0.6; 25.0.0 to before 36.0.6; 37.0.0 to before 40.0.4; 41.0.0 to before 41.0.4 Vulnerable ·bytecodealliance
Remediation
- Fix · CNA wasmtime (bytecodealliance) Fixed in 24.0.6, 36.0.6, 40.0.4, 41.0.4
- Fix · GHSA-852m-cvvp-9p4w wasmtime (crates.io) Fixed in 24.0.6 Advisory →
- Fix · GHSA-852m-cvvp-9p4w wasmtime (crates.io) Fixed in 36.0.6 Advisory →
- Fix · GHSA-852m-cvvp-9p4w wasmtime (crates.io) Fixed in 40.0.4 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 |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-27204
- 2026-10-03 Alias added: GHSA-852m-cvvp-9p4w
- 2026-10-09 EPSS moved to the 50th–90th percentile
- 2026-10-25 EPSS moved to the below the 50th percentile
References
Advisory 3
Other 7
- https://github.com/bytecodealliance/wasmtime/issues/11552
- https://docs.rs/wasmtime-wasi/latest/wasmtime_wasi/struct.WasiCtxBuilder.html#method.max_random_size
- https://docs.rs/wasmtime/latest/wasmtime/component/struct.ResourceTable.html#method.set_max_capacity
- https://docs.rs/wasmtime/latest/wasmtime/struct.Store.html#method.set_hostcall_fuel
- https://docs.wasmtime.dev/security-what-is-considered-a-security-vulnerability.html
- https://github.com/bytecodealliance/wasmtime
- https://rustsec.org/advisories/RUSTSEC-2026-0020.html
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-2026-27204 · CVE Program
- CVE-2026-27204 · NVD
- FIRST EPSS
- GHSA-852m-cvvp-9p4w · GitHub Advisory Database · CC BY 4.0
- CVE-2026-27204 · 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