CVE-2026-59940
Deserialization flaw in seroval (<1.5.3) enables RCE via crafted JSON Promise control nodes.
Is CVE-2026-59940 being exploited?
Not confirmed. CVE-2026-59940 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.61% probability of exploitation in the next 30 days.
How severe is CVE-2026-59940?
CVE-2026-59940 is rated Critical with a CVSS score of 9.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-59940?
Yes. A fix has been recorded for CVE-2026-59940. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-59940 affect?
CVE-2026-59940 affects seroval < 1.5.3, Node.js applications using seroval and plugins, Downstream frameworks registering callable wrappers. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-59940?
Upgrade seroval to >=1.5.3 and audit deserialization of untrusted data
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attacker-crafted JSON Promise nodes can trigger deserialization side effects, invoking server-side callables and enabling remote code execution.
Immediate action required
- affected< 1.5.3
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.