VulnerabilityPublished 21 Jan 2026

CVE-2026-23736: lxsmnsyc seroval · Prototype Pollution

Affects lxsmnsyc serovalSource CVE Database V5

Not known to be exploited · CVSS 7.3 High : upgrade to 1.4.1 soon.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

7.3High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 22% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.4.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 21 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade lxsmnsyc seroval to 1.4.1.

Affected software

Product	Affected	Fixed in
lxsmnsycseroval	Affected <1.4.1	Fixed in 1.4.1
npmseroval`pkg:npm/seroval`Other threats	Affected <1.4.1	Fixed in 1.4.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should immediately audit their software dependencies to identify usage of seroval versions below 1.4.1. Upgrading to seroval 1.4.1 or later is the primary and most effective mitigation. For environments where immediate upgrade is not feasible, implementing strict input validation and sanitization on JSON data before deserialization can reduce risk. Employ runtime application self-protection (RASP) or web application firewalls (WAFs) configured to detect and block prototype pollution attack patterns. Incorporate security testing in CI/CD pipelines to detect vulnerable library versions and prototype pollution attempts. Monitor logs for anomalous object prototype modifications and unusual application behavior. Educate developers about the risks of prototype pollution and secure coding practices related to object deserialization. Finally, maintain an incident response plan tailored to JavaScript application compromises to quickly contain and remediate any exploitation attempts.

Description

CVE-2026-23736 is a high-severity prototype pollution vulnerability in the seroval JavaScript value stringification library (versions below 1.4.1). The flaw arises from improper input validation during JSON deserialization, allowing attackers to modify object prototype attributes maliciously. Exploitation requires no authentication or user interaction and can be performed remotely over the network. Successful attacks can lead to partial compromise of confidentiality, integrity, and availability of affected applications. The vulnerability is fixed in seroval version 1.4.1. European organizations using vulnerable versions in their JavaScript environments should prioritize updating to mitigate risks.

Impact

For European organizations, this vulnerability poses a significant risk especially to those developing or deploying JavaScript applications that incorporate seroval for advanced serialization tasks. Exploitation could allow attackers to manipulate application logic, corrupt data, or cause service disruptions, impacting business continuity and data security. Organizations in sectors such as finance, healthcare, and critical infrastructure, which rely heavily on web applications and JavaScript frameworks, may face increased exposure. The vulnerability could also be leveraged in supply chain attacks targeting software development pipelines. Given the remote, unauthenticated exploitability, attackers could scan for vulnerable instances and compromise systems at scale. The partial impact on confidentiality and integrity could lead to data breaches or unauthorized modifications, while availability impacts might cause denial of service conditions. This could result in regulatory compliance issues under GDPR and other European data protection laws, leading to financial and reputational damage.

Summary

CVE-2026-23736 identifies a prototype pollution vulnerability in the seroval library, a tool designed to facilitate JavaScript value stringification beyond the capabilities of JSON.stringify. Specifically, versions 1.4.0 and earlier improperly validate input during JSON deserialization, allowing an attacker to inject malicious object keys that alter the prototype chain of JavaScript objects. This CWE-1321 vulnerability enables an attacker to manipulate the behavior of applications by corrupting object prototypes, potentially leading to arbitrary code execution, data tampering, or denial of service. The vulnerability is exploitable remotely without any authentication or user interaction, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N). The impact spans confidentiality, integrity, and availability, though the confidentiality and integrity impacts are partial, reflecting potential but not guaranteed data exposure or modification. The issue is limited to the JSON deserialization functionality of seroval and is resolved in version 1.4.1. While no known exploits have been reported in the wild, the vulnerability's characteristics suggest it could be leveraged in supply chain attacks or to compromise web applications relying on seroval for complex data serialization tasks.

CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (opens in a new tab)
Variant weakness
The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.
Implementation
By freezing the object prototype first (for example, Object.freeze(Object.prototype)), modification of the prototype becomes impossible.
Architecture and Design
By blocking modifications of attributes that resolve to object prototype, such as proto or prototype, this weakness can be mitigated.
Implementation · Input Validation
When handling untrusted objects, validating using a schema can be used.
OWASP Cheat Sheets
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V5.1.2 (opens in a new tab)
Attack patterns
Accessing Functionality Not Properly Constrained by ACLs (opens in a new tab)
Exploiting Incorrectly Configured Access Control Security Levels (opens in a new tab)
Manipulating User-Controlled Variables (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 29 Jan 2026, 08:52 UTC

WeaknessesCWE-1321

Technical details

References

Community reviews

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