WasmtimeApplication · Bytecodealliance
CVE-2026-34944
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedWasmtime 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceWasmtime's Cranelift compiler on x86-64 platforms with SSE3 disabled improperly handles the f64x2.splat WebAssembly instruction, loading 8 bytes beyond the intended boundary. This can cause uncaught segfaults from unmapped guard page access when signals-based traps are disabled, or potential out-of-sandbox memory reads when guard pages are disabled.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
WasmtimeApplication
< 24.0.7>= 25.0.0, < 36.0.7>= 37.0.0, < 42.0.2>= 43.0.0, < 43.0.1CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Wasmtime versionRun `wasmtime --version` or check the installed package version via your package manager (e.g., `cargo list wasmtime`, `pip show wasmtime`, etc.)Affected if The version is one of the affected ranges: < 24.0.7, 25.0.0 to < 36.0.7, 37.0.0 to < 42.0.2, or 43.0.0 to < 43.0.1
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Confirm x86-64 architectureRun `uname -m` or check CPU info via `/proc/cpuinfo` to verify the host is x86-64 (will show x86_64 or amd64)Affected if The architecture is not x86-64 (the flaw only affects x86-64 platforms)
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Determine if SSE3 is disabledCheck CPU flags via `grep -o 'sse3' /proc/cpuinfo` or inspect the runtime environment for CPU restrictions. For containerized environments, check for CPU flag restrictions (e.g., `--cpu-flags` in Docker, or seccomp/syscall filters that disable SSE3)Affected if SSE3 is explicitly disabled or unavailable - this is required for the vulnerability to trigger
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Verify signal-based trap configurationInspect Wasmtime configuration or runtime flags. Check if `--trap-handler=disabled` or equivalent configuration is set, or review environment variables like `WASMTIME_BACKTRACES` being set to false. Look at the execution context for signal handling configurationAffected if Signal-based traps are disabled, which would cause uncaught segfaults from unmapped guard page access
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Check if guard pages are disabledReview Wasmtime instantiation settings or compiled configuration for memory guard settings. Check for flags like `--disable-guarded-memory` or memory configuration that disables guard pagesAffected if Guard pages are disabled in the Wasmtime runtime configuration, creating potential for out-of-sandbox memory reads
You are affected if you run Wasmtime on x86-64 with SSE3 disabled using an affected version, combined with either disabled signal-based traps or disabled guard pages in your runtime configuration.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped24.0.736.0.742.0.2
Upgrade Wasmtime to version 24.0.7, 36.0.7, 42.0.1, or 43.0.1 or later to obtain the patched Cranelift compiler.
Upgrade to Wasmtime 24.0.7, 36.0.7, 42.0.2, or 43.0.1 depending on your current version branch
- Identify the currently installed Wasmtime version using cargo list wasmtime or the project's dependency file
- Determine which version branch you are on (24.x, 25-36.x, 37-42.x, or 43.x)
- For Wasmtime < 24.0.7: upgrade to version 24.0.7
- For Wasmtime >= 25.0.0 and < 36.0.7: upgrade to version 36.0.7
- For Wasmtime >= 37.0.0 and < 42.0.2: upgrade to version 42.0.2
- For Wasmtime >= 43.0.0 and < 43.0.1: upgrade to version 43.0.1
- Update the dependency in Cargo.toml (e.g., wasmtime = "24.0.7") or lockfile
- Run cargo update wasmtime to update the lockfile
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Wasmtime
Scoped from the published advisory
- Consultation4.0 h
- Implementation2.0 h
- Testing8.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,928.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-34944 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-34944 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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