CVE-2026-58592
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 · uneditedLadybird contains a dangling-reference memory-safety flaw in its WebAssembly ESM-integration module loader. When a JavaScript function is imported into a WebAssembly module via the ESM path, WebAssemblyModule.cpp passes a stack-local Wasm::FunctionType by reference to create_host_function, whose host callback captures and later reads that reference; once the ESM link-loop iteration ends the FunctionType is destroyed, leaving the callback with a dangling reference (the normal instantiate path uses a long-lived reference and is not affected). Stale result-type data lets the host callback return an empty result vector for a statically non-empty result, so the destination register retains an attacker-influenced value that is then consumed by the WASM-GC array.set handler, which bit-casts the reference low bits to an ArrayInstance pointer after only a null check, yielding an arbitrary write. A web page can chain this into code execution in the WebContent process. Verified reachable from HTML content without any instrumentation or source modification.
In the news
Third-party coverageSurfaced from public web coverage — external links open in a new tab.
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 confidenceLadybird browser contains a dangling-reference memory-safety flaw in WebAssemblyModule.cpp where a stack-local Wasm::FunctionType is passed by reference to create_host_function during ESM import. When the ESM link-loop iteration ends, the FunctionType is destroyed but the host callback retains a dangling reference, causing it to return an empty result vector. This leaves attacker-influenced values in registers that the WASM-GC array.set handler then bit-casts to an ArrayInstance pointer after only a null check, enabling arbitrary write primitives reachable from HTML content.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS 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
- High
- Privileges
- None
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/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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Confirm Ladybird browser installationCheck for the Ladybird executable (e.g., 'ladybird' binary or 'Browser' application bundle) in common locations such as /usr/bin/ladybird, /Applications/Ladybird.app on macOS, or via command: which ladybirdAffected if Ladybird browser is not installed on the system
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Identify Ladybird versionRun 'ladybird --version' or check the application bundle info for version metadata. Compare the version number against any released versions that include the fix for WebAssemblyModule.cppAffected if Unable to determine version or version predates the fix for the dangling reference in ESM import handling
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Verify WebAssembly module support is enabledCheck Ladybird configuration or runtime settings for WebAssembly (WASM) support. This may be found in preferences, about:config, or by inspecting compiled feature flags if accessibleAffected if WebAssembly support is enabled (the vulnerability requires WASM to be functional to trigger the arbitrary write primitive)
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Determine if ESM import with WebAssembly is usedInspect any local web content, extensions, or test cases that load WebAssembly modules via ES6 import statements ('import' from .wasm files). Review application logs or network traffic for ESM-to-WASM import patternsAffected if The system processes or renders HTML content that uses ESM imports to load WebAssembly modules (the vulnerable code path is triggered during ESM link-loop iteration)
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Inspect WebAssemblyModule.cpp for the vulnerability patternIf source code access is available, examine WebAssemblyModule.cpp for stack-local Wasm::FunctionType passed by reference to create_host_function within ESM import handling code. Look for absence of heap allocation or long-lived scope for FunctionType in the ESM path versus the normal instantiate pathAffected if Source code shows the vulnerable pattern: stack-local FunctionType with insufficient lifetime during ESM link-loop iteration
The environment is affected if Ladybird browser is installed with a version that predates the fix, WebAssembly is enabled, and the system processes HTML content using ESM imports to load WebAssembly modules.
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.
From vendor dataFix the dangling reference by ensuring the Wasm::FunctionType has sufficient lifetime during the ESM import path, mirroring the long-lived reference pattern used in the unaffected normal instantiate path; consider using heap allocation or moving the FunctionType to a longer-lived scope.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2026-58592 — 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-2026-58592 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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