CVE-2026-25521 locutusjs CVE debrief

Who should care

Developers and administrators using Locutus versions between 2.0.12 and 2.0.39 should be aware of this critical vulnerability. Given the high CVSS score, immediate attention is required to prevent potential exploitation. This vulnerability could allow attackers to manipulate the Object.prototype, potentially leading to security issues in applications using Locutus.

Technical summary

The CVE-2026-25521 vulnerability in Locutus is caused by a prototype pollution issue. This occurs when an attacker can modify the prototype of an object, in this case, Object.prototype, using a crafted input through String.prototype. The vulnerability has a CVSS score of 9.4, indicating critical severity. It affects Locutus versions from 2.0.12 up to but not including 2.0.39. The issue was initially mitigated but not fully resolved, allowing for continued exploitation. The fix in version 2.0.39 addresses this vulnerability by properly preventing prototype pollution.

Defensive priority

High. Immediate action is required to update affected installations of Locutus to version 2.0.39 or later to prevent potential exploitation of this critical vulnerability.

Recommended defensive actions

• Update Locutus to version 2.0.39 or later.
• Review and inventory applications using Locutus to ensure they are not exposed.
• Implement monitoring to detect potential exploitation attempts.
• Consider compensating controls if immediate update is not feasible.
• Track vendor advisories for further information.

Evidence notes

The CVE-2026-25521 vulnerability details were obtained from the NVD and CVE.org. The vulnerability affects Locutus versions between 2.0.12 and 2.0.39. A patch is available in version 2.0.39. Additional information and references can be found in the source item and resource links provided.

Official resources