# CVE-2026-121970: Pay with Vipps and MobilePay for WooCommerce before 6.4.1 Webhook Signature Forgery

Status: published. Published: 2026-11-04. Updated: 2026-11-04.

Pay with Vipps and MobilePay for WooCommerce (woo-vipps) before 6.4.1 contains an improper cryptographic signature verification vulnerability in the recurring-payment webhook handler that allows unauthenticated attackers to forge webhook requests when no local webhook secret is stored, because the code fails to return on an empty secret and computes an HMAC keyed with an empty string using a loose == comparison instead of hash_equals. Attackers can craft a recurring.agreement-stopped.v1 event with a known agreementId and a matching empty-key signature to cancel a victim's active WooCommerce subscription.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://wordpress.org/plugins/woo-vipps/#developers

## Affected products and versions

- wphostingdev / Pay with Vipps and MobilePay for WooCommerce: ≥ 5.0.0; < 6.4.1 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 6.3 (medium); CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 3.7 (low); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-347

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://wordpress.org/plugins/woo-vipps/#developers (CNA: VulnCheck; patch, release-notes)

- https://plugins.trac.wordpress.org/browser/woo-vipps/trunk/recurring/changelog.txt (CNA: VulnCheck)

- https://plugins.trac.wordpress.org/browser/woo-vipps/trunk/recurring/includes/wc-vipps-recurring.php (CNA: VulnCheck)

- https://www.vulncheck.com/advisories/pay-with-vipps-and-mobilepay-for-woocommerce-before-webhook-signature-forgery (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-121970; retrieved 2026-11-04; source updated 2026-11-04

Revision: 1d1f79815f8db3ca77e60119ab0e66cf96480dba760271a8d194e2cdd602f22f

Canonical: https://y2.dev/cve/CVE-2026-121970

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.