CVE-2026-59940Network attack vector

Server-side invocation via Promise resolver confusion

Published Aug 18, 2026 · Updated Aug 18, 2026

Deserialization of untrusted data in lxsmnsyc seroval before 1.5.3 allows remote attackers to trigger server-side invocation via crafted JSON. In fromJSON(), Promise control nodes operate on values from the general deserialization reference table without verifying that the referenced values are genuine internal Promise resolver records. Exposure requires deserialization of untrusted Seroval JSON with plugins enabled; downstream frameworks that register callable wrappers can turn this primitive into unintended server-side invocation and potentially remote code execution.

CVSS severity9.8
Critical
EPSS probability0.61%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Deserialization of untrusted data in lxsmnsyc seroval before 1.5.3 allows remote attackers to trigger server-side invocation via crafted JSON. In fromJSON(), Promise control nodes operate on values from the general deserialization reference table without verifying that the referenced values are genuine internal Promise resolver records. Exposure requires deserialization of untrusted Seroval JSON with plugins enabled; downstream frameworks that register callable wrappers can turn this primitive into unintended server-side invocation and potentially remote code execution.

The record

CVE
CVE-2026-59940
Published
Aug 18, 2026
Updated
Aug 18, 2026
Vendor
lxsmnsyc
Product
seroval
Classifications
CWE-502, CWE-843
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.5.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

lxsmnsyc · serovalversion=< 1.5.3

Published CVSS scores

9.8GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-502Deserialization of Untrusted Data
CWE-843Access of Resource Using Incompatible Type ('Type Confusion')

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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