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Fencer Vulns
high 8.6

CVE-2024-43357 json

JavaScript specification issue may lead to type confusion and pointer dereference in implementations

published 2024-08-15 2 y ago modified 2026-06-17 4 mo ago also EUVD-2024-40246

cvss
8.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 52%
public exploits
0
none known

Summary

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

Patch / fix

  • ecma_international ecma262 2025

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
2 y ago

Exploit prediction

0.68% chance of exploitation in the next 30 days, higher than 52% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

Affected products

  • tc39 ecma262
  • ecma_international ecma262

Classification

Weakness
  • CWE-248 Uncaught Exception
  • CWE-476 NULL Pointer Dereference
  • CWE-843 Access of Resource Using Incompatible Type

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.