# CVE-2026-76842: Mercado Pago Node.js SDK through 3.4.0 Path Injection via Unencoded Identifiers in Payment Clients

> Attackers can manipulate payment identifiers to access or modify other merchant resources via path traversal in the Mercado Pago Node.js SDK.

- **Severity:** High 8.8 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Aug 2026
- **Updated:** 29 Aug 2026
- **Also known as:** GHSA-8vxq-h2gr-x277

## What is CVE-2026-76842?

CVE-2026-76842 is a high-severity path traversal vulnerability in mercadopago, published on 24 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-76842?


## How do I fix CVE-2026-76842?

No fix has been published for CVE-2026-76842 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-76842 being exploited?

There is no known exploitation of CVE-2026-76842 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-76842 and fix it if it is affected.

What it is: CVE-2026-76842 is a high-severity path traversal vulnerability in mercadopago, published on 24 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-76842 in the wild and no public exploit code.

Affected product: mercadopago. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-76842/ (Markdown: https://insights.sbomify.com/CVE-2026-76842/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-76842
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-76842
- OSV: https://osv.dev/vulnerability/CVE-2026-76842

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-76842/
Summaries are generated and may contain mistakes; the official description above is the record.