CVE-2026-25521Public exploit

Object prototype pollution via hijacked includes guard

Published Feb 4, 2026 · Updated Feb 4, 2026

Prototype pollution in Locutus 2.0.12 through 2.0.38 allows local users to modify Object.prototype through crafted parse_str input. The parse_str function calls the writable String.prototype.includes method to reject forbidden keys, so replacing that method bypasses the guard. Exploitation requires JavaScript execution in the same process and a crafted constructor[prototype] key; downstream gadgets determine the resulting consequence.

CVSS severity9.4
Critical
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Prototype pollution in Locutus 2.0.12 through 2.0.38 allows local users to modify Object.prototype through crafted parse_str input. The parse_str function calls the writable String.prototype.includes method to reject forbidden keys, so replacing that method bypasses the guard. Exploitation requires JavaScript execution in the same process and a crafted constructor[prototype] key; downstream gadgets determine the resulting consequence.

The record

CVE
CVE-2026-25521
Published
Feb 4, 2026
Updated
Feb 4, 2026
Vendor
Locutus
Product
Locutus
Classifications
CWE-915, CWE-1321
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 4, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 4, 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=>= 2.0.12, < 2.0.39

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Locutus · Locutusversion=>= 2.0.12, < 2.0.39

Published CVSS scores

9.4GitHub, Inc.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
9.3Red Hat Product SecurityCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
8.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

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

Weakness, pattern, technique

CWE-915Improperly Controlled Modification of Dynamically-Determined Object Attributes
CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Public exploit references

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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