Security readout for executives and security teams
Plain-English summary
Wasmtime hosts running untrusted WebAssembly with WASI may let a guest consume excessive host resources, causing service disruption. The issue affects multiple pre-fixed Wasmtime branches. Fixes exist, but some fixed versions require explicit configuration to enforce protective limits; Wasmtime 42.0.0 and later tunes these by default.
Executive priority
Treat as a timely availability-risk update for platforms using Wasmtime with untrusted WebAssembly. It is not currently evidenced as actively exploited, but affected multi-tenant or customer-facing execution environments should be prioritized because a guest may disrupt host service availability.
Technical view
CVE-2026-27204 is a resource exhaustion flaw in Wasmtime WASI host interfaces. Guest-controlled requests were not sufficiently bounded, enabling denial of service against host availability. Affected ranges include versions before 24.0.6, 25.x before 36.0.6, 37.x before 40.0.4, and 41.x before 41.0.4. Related controls include random-size limits, resource table capacity, and hostcall fuel.
Likely exposure
Exposure is most relevant for applications embedding Wasmtime and allowing potentially malicious or tenant-controlled WebAssembly guests using WASI. Internal-only, trusted-module deployments have lower practical risk. The source bundle does not indicate broad internet scanning or automatic exploitation.
Exploitation context
The advisory describes a denial-of-service condition, not code execution or data theft. CVSS lists low attack complexity but requires privileges, user interaction, and a present attack requirement. CISA KEV status is false in the provided data, and no cited source claims active exploitation.
Researcher notes
The fix is released across maintained branches, but the advisory notes default behavior in fixed versions may not fully prevent the issue until 42.0.0 and later. Validation should focus on embedding configuration, WASI exposure, and guest trust boundaries. Evidence is insufficient to claim exploitation in the wild.
Mitigation direction
- Upgrade Wasmtime to 24.0.6, 36.0.6, 40.0.4, 41.0.4, or 42.0.0 or later.
- For fixed versions before 42.0.0, configure resource-limiting knobs as appropriate for your embedding.
- Review WASI limits including random size, resource table capacity, and hostcall fuel settings.
- Prioritize systems executing untrusted, third-party, or multi-tenant WebAssembly guests.
- If unable to upgrade, check Bytecode Alliance guidance; sources state no known workaround without upgrading.
Validation and detection
- Inventory services embedding Wasmtime and identify the linked runtime version.
- Confirm whether the application enables WASI host interfaces for guest modules.
- Determine whether guests are trusted, third-party, user-supplied, or multi-tenant.
- Verify fixed versions are deployed in build manifests, lockfiles, containers, and runtime artifacts.
- Review embedding code for configured resource limits after upgrading.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CWE-400: Exact CWE lookup
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Open ATT&CK lookupCWE-770: Exact CWE lookup
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Open ATT&CK lookupCWE-774: Exact CWE lookup
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Open ATT&CK lookupCWE-789: Exact CWE lookup
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Open ATT&CK lookupCVE-2026-27204 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.9 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
6.9MediumVector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-852m-cvvp-9p4wCVE reference · x_refsource_CONFIRM
- https://github.com/bytecodealliance/wasmtime/issues/11552CVE reference · x_refsource_MISC
- https://github.com/bytecodealliance/wasmtime/pull/12599CVE reference · x_refsource_MISC
- https://docs.rs/wasmtime-wasi/latest/wasmtime_wasi/struct.WasiCtxBuilder.html#method.max_random_sizeCVE reference · x_refsource_MISC
- https://docs.rs/wasmtime/latest/wasmtime/component/struct.ResourceTable.html#method.set_max_capacityCVE reference · x_refsource_MISC
- https://docs.rs/wasmtime/latest/wasmtime/struct.Store.html#method.set_hostcall_fuelCVE reference · x_refsource_MISC
- https://docs.wasmtime.dev/security-what-is-considered-a-security-vulnerability.htmlCVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.