CVE-2026-104846 · GHSA-p6vx-979v-rg4c

Seroval: `fromJSON()` Promise thenable assimilation invokes plugin-produced callables (bypass of GHSA-mv8w-475r-vwqw)

Risk score: 74/100
CVSS: 9.8 v3.1
Exploit chance (30 days): 0.3%
Published: 2 Oct 2026

Open in the live forecast Today's forecast

What to know

What it is: Seroval facilitates JS value stringification, including complex structures beyond JSON.stringify capabilities. From 0.12.0 until 1.6.2, fromJSON deserialization of a fulfilled Promise control node can pass a plugin-produced callable-bearing thenable to a native Promise resolver. ECMAScript thenable assimilation then i…
Affected: seroval (npm) >= 0.12.0, <= 1.6.0
Fix: Upgrade seroval to 1.6.2 or later.
Exploitation: No known exploitation

Story map

Story map: the flaws, the fix, how it unfolded and what it connects to. Boxes link to the record or article.

At a glance

seroval: Amber, patch this week. Seroval facilitates JS value stringification, including complex structures beyond JSON.stringify capabilities. From 0.12.0 until 1.6.2, fromJSON deserialization of a fulfilled Promise control node can pass a plugin-produced callable-bearing thenable to a native Promise resolver. ECMAScript thenable assimilation then i…

The flaws

CVE-2026-104846: Seroval: `fromJSON()` Promise thenable assimilation invokes plugin-produced callables (bypass of GHSA-mv8w-475r-vwqw) (CVSS 9.8 · EPSS 0%)
CVE-2026-104845: Seroval: Memory exhaustion via unchecked TypedArray length in JSON deserialization (CVSS 7.5 · EPSS 0%)

The fix

Upgrade seroval: 1.6.2 · 1.6.3 or later on your release line

Who is exposed: seroval (npm) >= 0.12.0, <= 1.6.0

Where it stands

No known exploitation

Connects to

Same weakness: CWE-843 (CWE-843). 61 other warnings in 30 days

Why it is Amber

CVSS 9.8 critical
Remotely exploitable without logging in
On your watchlist: npm

Affected packages

Package	Ecosystem	Vulnerable	Fixed in
seroval	npm	>= 0.12.0, <= 1.6.0	1.6.2

References

Original description

Seroval facilitates JS value stringification, including complex structures beyond JSON.stringify capabilities. From 0.12.0 until 1.6.2, fromJSON deserialization of a fulfilled Promise control node can pass a plugin-produced callable-bearing thenable to a native Promise resolver. ECMAScript thenable assimilation then invokes the callable unexpectedly, allowing attacker-controlled JSON to trigger code in applications using plugin-capable Seroval releases. This path bypasses the Promise resolver type-confusion remediation in version 1.5.3 for CVE-2026-59940 because the unexpected invocation occurs through native Promise settlement after the referenced value is deserialized. This issue is fixed in version 1.6.2.

Last activity 2 Oct 2026. Patch Forecast updates every hour.