Mercado Pago SDK up to 3.4.0 API Request Path index.ts RestClient.fetch ID redirect

Summaryinfo

A vulnerability was found in Mercado Pago SDK up to 3.4.0 and classified as problematic. The affected element is the function RestClient.fetch of the file src/clients/payment/get/index.ts of the component API Request Path. Such manipulation of the argument ID leads to redirect. This vulnerability is traded as CVE-2026-76842. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in Mercado Pago SDK up to 3.4.0 and classified as problematic. Affected by this issue is the function RestClient.fetch of the file src/clients/payment/get/index.ts of the component API Request Path. The manipulation of the argument id with an unknown input leads to a redirect vulnerability. Using CWE to declare the problem leads to CWE-601. A web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a Redirect. This simplifies phishing attacks. Impacted is integrity. CVE summarizes:

The Mercado Pago Node.js SDK interpolates caller-supplied identifiers into API request paths without percent-encoding them, so characters that are structural in a URL survive into the outgoing request. The payment (get, capture, cancel), paymentRefund (create, total, list, get), advancedPayment (get, capture, cancel, update, updateReleaseDate) and disbursementRefund (create, createAll, listAll) clients build their path as a template literal, for example RestClient.fetch(`/v1/payments/${id}`, ...) in src/clients/payment/get/index.ts. A dot-dot or slash sequence in the identifier is normalised by the WHATWG URL parser and redirects the request to a different endpoint, and a question mark appends attacker-chosen query parameters, in both cases carrying the merchant's own access token. An application that forwards an identifier influenced by an untrusted party into one of these methods without an ownership check therefore allows that party to reach other resources within the merchant's token scope. The repository already contains the intended helper, encodePathParam in src/utils/path.ts, which pull request 451 applied to roughly 29 other clients while leaving these unchanged.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-76842 since 08/19/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1204.001.

Applying the patch 451 is able to eliminate this problem.

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Productinfo

Vendor

• Mercado Pago

Name

• SDK

Version

• 3.0
• 3.1
• 3.2
• 3.3
• 3.4.0

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