[Pkg-javascript-devel] Bug#1131462: node-flatted: CVE-2026-33228

[Salvatore Bonaccorso]

Source: node-flatted
Version: 3.4.1~ds-1
Severity: important
Tags: security upstream
X-Debbugs-Cc: carnil at debian.org, Debian Security Team <team at security.debian.org>

Hi,

The following vulnerability was published for node-flatted.

CVE-2026-33228[0]:
| flatted is a circular JSON parser. Prior to version 3.4.2, the
| parse() function in flatted can use attacker-controlled string
| values from the parsed JSON as direct array index keys, without
| validating that they are numeric. Since the internal input buffer is
| a JavaScript Array, accessing it with the key "__proto__" returns
| Array.prototype via the inherited getter. This object is then
| treated as a legitimate parsed value and assigned as a property of
| the output object, effectively leaking a live reference to
| Array.prototype to the consumer. Any code that subsequently writes
| to that property will pollute the global prototype. This issue has
| been patched in version 3.4.2.


If you fix the vulnerability please also make sure to include the
CVE (Common Vulnerabilities & Exposures) id in your changelog entry.

For further information see:

[0] https://security-tracker.debian.org/tracker/CVE-2026-33228
    https://www.cve.org/CVERecord?id=CVE-2026-33228
[1] https://github.com/WebReflection/flatted/security/advisories/GHSA-rf6f-7fwh-wjgh
[2] https://github.com/WebReflection/flatted/commit/885ddcc33cf9657caf38c57c7be45ae1c5272802

Please adjust the affected versions in the BTS as needed.

Regards,
Salvatore