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

> A dangling reference in Ladybird's WebAssembly loader allows arbitrary writes and code execution via malicious web content.

- **Severity:** High 8.9 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 1 Jul 2026
- **Updated:** 11 Sep 2026
- **Also known as:** GHSA-vm9p-mx69-hf3f

## What is CVE-2026-58592?

CVE-2026-58592 is a high-severity use after free vulnerability in LadybirdBrowser Ladybird, published on 1 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-843 (Access of Resource Using Incompatible Type), CWE-825 (Expired Pointer Dereference), CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-58592?


## How do I fix CVE-2026-58592?

No fix has been published for CVE-2026-58592 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-58592 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-58592 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-58592 and fix it if it is affected.

What it is: CVE-2026-58592 is a high-severity use after free vulnerability in LadybirdBrowser Ladybird, published on 1 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-58592 exists.

Affected product: LadybirdBrowser Ladybird. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-58592/ (Markdown: https://insights.sbomify.com/CVE-2026-58592/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-58592
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-58592
- OSV: https://osv.dev/vulnerability/CVE-2026-58592

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-58592/
Summaries are generated and may contain mistakes; the official description above is the record.