CVE-2026-26021VulnerabilityPublished 11 Feb 2026

CVE-2026-26021: ahdinosaur set-in · Prototype Pollution

Affects ahdinosaur set-inSource CVE Database V5

Not known to be exploited · CVSS 9.4 Critical : upgrade to 2.0.5 as a priority.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 4.0 base score

9.4Critical

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

EPSS: 0.5% chance of exploitation in 30 days – higher than 46% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.0.5

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

Attack Vector: Local
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: High
Vulnerable system integrity: High
Vulnerable system availability: High
Subsequent system confidentiality: High
Subsequent system integrity: High
Subsequent system availability: High

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

Attack Vector: Local: The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: High: There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Vulnerable system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the vulnerable system.
Vulnerable system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Vulnerable System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).
Subsequent system confidentiality: High: There is a total loss of confidentiality, resulting in all resources within the Subsequent System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Subsequent system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the Subsequent System. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the Subsequent System.
Subsequent system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Subsequent System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Subsequent System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 11 Feb 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 2026-10-25.

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 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 ahdinosaur set-in to 2.0.5.

Affected software

Product	Affected	Fixed in
ahdinosaurset-in	Affected >=2.0.1 <2.0.5	Fixed in 2.0.5

AI-suggested

To mitigate this vulnerability, organizations should immediately upgrade the 'set-in' package to version 2.0.5 or later, where the prototype pollution issue is fixed. Additionally, developers should audit their dependency trees to identify any indirect usage of vulnerable versions and update those accordingly. Implementing strict input validation and sanitization can reduce the risk of malicious payloads reaching vulnerable code paths. Employing runtime protections such as JavaScript sandboxing or integrity checks can help detect or prevent prototype pollution attacks. Monitoring application logs and behavior for anomalies related to object prototype modifications can provide early detection of exploitation attempts. Finally, integrating automated dependency scanning tools into the CI/CD pipeline will help catch vulnerable packages before deployment.

Description

set-in provides the set value of nested associative structure given array of keys. A prototype pollution vulnerability exists in the the npm package set-in (>=2.0.1, < 2.0.5). Despite a previous fix that attempted to mitigate prototype pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using Array.prototype. This has been fixed in version 2.0.5.

Impact

The impact of this vulnerability is substantial for organizations using the 'set-in' package in their software stacks. Prototype pollution can lead to widespread application instability, unauthorized code execution, and data integrity issues. Attackers can manipulate the global object prototype, affecting all objects and potentially bypassing security controls or causing application crashes. This can result in data breaches, service outages, and compromised systems. Since 'set-in' is a utility package often used in web applications and backend services, exploitation could affect a broad range of environments, including cloud services, enterprise applications, and developer tools. The lack of required authentication and user interaction lowers the barrier for exploitation, increasing the risk. Organizations that do not promptly patch may face increased exposure to targeted attacks or automated exploit attempts once public exploits emerge.

Summary

The vulnerability identified as CVE-2026-26021 affects the 'set-in' npm package, specifically versions from 2.0.1 up to but not including 2.0.5. 'set-in' is a utility that sets values in nested associative data structures based on an array of keys. The flaw is a prototype pollution vulnerability categorized under CWE-1321, which involves improper control over modifications to object prototype attributes. Despite a prior fix that attempted to block user inputs containing forbidden keys to prevent pollution, attackers can still exploit the vulnerability by crafting inputs that leverage Array.prototype. This bypass allows an attacker to inject or modify properties on Object.prototype, potentially altering the behavior of all objects in the JavaScript environment. Such pollution can lead to arbitrary code execution, denial of service, or data corruption. The vulnerability has a CVSS 4.0 base score of 9.4, indicating critical severity, with a local attack vector and no required privileges or user interaction. The fix was implemented in version 2.0.5, which properly addresses the prototype pollution vector. No public exploits have been reported yet, but the risk remains high due to the critical nature of the vulnerability and the common usage of the package in Node.js applications.

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

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 19 Feb 2026, 13:57 UTC

WeaknessesCWE-1321

Technical details

References

Community reviews

Related threats