CVE-2026-42044: Axios: Invisible JSON Response Tampering via Prototype Pollution Gadget in `parseReviver`

Vulnerability summary

CVE-2026-42044 is a critical (CVSS 9.1) vulnerability in axios. EPSS estimates a 0.62% chance of exploitation in the next 30 days, higher than 49.6% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 24-04-2026
   PublishedVulnerability first disclosed.
2. 10-09-2026
   Last modifiedVulnerability information updated.

Description

Axios is a promise based HTTP client for the browser and Node.js. From 1.0.0 to before 1.15.2, he Axios library is vulnerable to a Prototype Pollution "Gadget" attack that allows any Object.prototype pollution in the application's dependency tree to be escalated into surgical, invisible modification of all JSON API responses — including privilege escalation, balance manipulation, and authorization bypass. The default transformResponse function at lib/defaults/index.js:124 calls JSON.parse(data, this.parseReviver), where this is the merged config object. Because parseReviver is not present in Axios defaults, not validated by assertOptions, and not subject to any constraints, a polluted Object.prototype.parseReviver function is called for every key-value pair in every JSON response, allowing the attacker to selectively modify individual values while leaving the rest of the response intact. This vulnerability is fixed in 1.15.2.

• CWE-915Improperly Controlled Modification of Dynamically-Determined Object AttributesThe product receives input from an upstream component that specifies multiple attributes, properties, or fields that are to be initialized or updated in an object, but it does not properly control which attributes can be modified.
• CWE-1321Improperly Controlled Modification of Object Prototype AttributesThe 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.