# CVE-2024-43357: JavaScript specification issue may lead to type confusion and pointer dereference in implementations

> A specification flaw in async generators allows type confusion and pointer dereference, potentially enabling code execution or crashes in JavaScript engines.

- **Severity:** High 8.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 Aug 2024
- **Updated:** 15 Aug 2024

## What is CVE-2024-43357?

CVE-2024-43357 is a high-severity memory corruption vulnerability in tc39 ecma262, published on 15 Aug 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

ECMA-262 is the language specification for the scripting language ECMAScript. A problem in the ECMAScript (JavaScript) specification of async generators, introduced by a May 2021 spec refactor, may lead to mis-implementation in a way that could present as a security vulnerability, such as type confusion and pointer dereference.

The internal async generator machinery calls regular promise resolver functions on IteratorResult (`{ done, value }`) objects that it creates, assuming that the IteratorResult objects will not be then-ables. Unfortunately, these IteratorResult objects inherit from `Object.prototype`, so these IteratorResult objects can be made then-able, triggering arbitrary behaviour, including re-entering the async generator machinery in a way that violates some internal invariants.

The ECMAScript specification is a living standard and the issue has been addressed at the time of this advisory's public disclosure. JavaScript engine implementors should refer to the latest specification and update their implementations to comply with the `AsyncGenerator` section.

## References

- https://github.com/tc39/ecma262/commit/1e24a286d0a327d08e1154926b3ee79820232727
- https://bugzilla.mozilla.org/show_bug.cgi?id=1901411
- https://github.com/boa-dev/boa/security/advisories/GHSA-f67q-wr6w-23jq
- https://bugs.webkit.org/show_bug.cgi?id=275407
- https://issues.chromium.org/issues/346692561
- https://www.cve.org/CVERecord?id=CVE-2024-7652

Weakness: CWE-843 (Access of Resource Using Incompatible Type), CWE-476 (NULL Pointer Dereference), CWE-248 (Uncaught Exception)

## Which versions are affected by CVE-2024-43357?


## How do I fix CVE-2024-43357?

No fix has been published for CVE-2024-43357 yet. Limit exposure of the affected software until one is available.

## Is CVE-2024-43357 being exploited?

There is no known exploitation of CVE-2024-43357 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-43357 and fix it if it is affected.

What it is: CVE-2024-43357 is a high-severity memory corruption vulnerability in tc39 ecma262, published on 15 Aug 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2024-43357 in the wild and no public exploit code.

Affected product: tc39 ecma262. 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-2024-43357/ (Markdown: https://insights.sbomify.com/CVE-2024-43357/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-43357
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-43357
- OSV: https://osv.dev/vulnerability/CVE-2024-43357

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From sbomify Insights: https://insights.sbomify.com/CVE-2024-43357/
Summaries are generated and may contain mistakes; the official description above is the record.