Vulnerability · Published Aug 18, 2026 · Assigned by GitHub_M

CVE-2026-59940Seroval: `seroval.fromJSON()` Promise resolver type confusion invokes attacker-controlled methods during deserialization

Critical 9.8

In plain English

A critical-severity unsafe deserialization in seroval from lxsmnsyc. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 57% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)9.8Critical

Exploit odds (30 days)0.8%top 42.8% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Seroval facilitates JS value stringification, including complex structures beyond JSON.stringify capabilities. Prior to 1.5.3, seroval.fromJSON() allows attacker-controlled JSON Promise control nodes to operate on values from the general deserialization reference table without verifying genuine internal Promise resolver records, causing deserialization side effects with plugins enabled and potentially unintended server-side invocation or remote code execution when downstream frameworks register callable wrappers. This issue is fixed in version 1.5.3.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	seroval	1.5.3	GHSA-mv8w-475r-vwqw

Affected products (as reported)

Vendor	Product	Versions
lxsmnsyc	seroval	< 1.5.3

Weakness: CWE-502, CWE-843 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

https://github.com/lxsmnsyc/seroval/security/advisories/GHSA-mv8w-475r-vwqw x_refsource_CONFIRM