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Lychee: Webshop checkout lets the client override the payment `amount` sent to the gateway via malicious crafted POST request

Type: advisorySources: OSV

Lychee is a free, open-source photo-management tool. Prior to 7.7.1, the Supporter or Pro webshop POST /api/v2/Shop/Checkout/Process flow accepts an unrestricted additional_data array and CheckoutService::preparePurchaseParameters() merges it after server-computed purchase parameters. Because later string keys overwrite earlier keys, an unauthenticated buyer can replace amount, currency, returnUrl, cancelUrl, or transactionId before CheckoutService::processPayment() passes the parameters to a non-PayPal Omnipay gateway. An attacker can therefore make a gateway accept a successful payment for an attacker-selected amount and obtain auto-fulfilled goods while underpaying the merchant. The issue requires an enabled webshop, a purchasable item, and an affected Omnipay gateway. This issue is fixed in version 7.7.1.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-77470
Confirmed fixed CVEs
Not specified
Updated in this feed
7 Nov 2026, 06:13 UTC · Revision 1

Source evidence

Lychee: Webshop checkout lets the client override the payment `amount` sent to the gateway via malicious crafted POST request

core-osv · Original source

Published 15 Oct 2026, 16:36 UTC

Lychee is a free, open-source photo-management tool. Prior to 7.7.1, the Supporter or Pro webshop POST /api/v2/Shop/Checkout/Process flow accepts an unrestricted additional_data array and CheckoutService::preparePurchaseParameters() merges it after server-computed purchase parameters. Because later string keys overwrite earlier keys, an unauthenticated buyer can replace amount, currency, returnUrl, cancelUrl, or transactionId before CheckoutService::processPayment() passes the parameters to a non-PayPal Omnipay gateway. An attacker can therefore make a gateway accept a successful payment for an attacker-selected amount and obtain auto-fulfilled goods while underpaying the merchant. The issue requires an enabled webshop, a purchasable item, and an affected Omnipay gateway. This issue is fixed in version 7.7.1.

osv:CVE-2026-77470
Complete source record
{
  "id": "fa4c65d20d68373b35f38270ea7de80156d101d6c760c7c3097d2f35fca4b730",
  "url": "https://osv.dev/vulnerability/CVE-2026-77470",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Lychee: Webshop checkout lets the client override the payment `amount` sent to the gateway via malicious crafted POST request",
    "summary": "Lychee is a free, open-source photo-management tool. Prior to 7.7.1, the Supporter or Pro webshop POST /api/v2/Shop/Checkout/Process flow accepts an unrestricted additional_data array and CheckoutService::preparePurchaseParameters() merges it after server-computed purchase parameters. Because later string keys overwrite earlier keys, an unauthenticated buyer can replace amount, currency, returnUrl, cancelUrl, or transactionId before CheckoutService::processPayment() passes the parameters to a non-PayPal Omnipay gateway. An attacker can therefore make a gateway accept a successful payment for an attacker-selected amount and obtain auto-fulfilled goods while underpaying the merchant. The issue requires an enabled webshop, a purchasable item, and an affected Omnipay gateway. This issue is fixed in version 7.7.1.",
    "evidence": "osv:CVE-2026-77470",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-77470",
      "aliases": [
        "CVE-2026-77470",
        "GHSA-476v-jr53-8rxc"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/lycheeorg/lychee",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "24e6e11f1da131ed20b192d7d7b7ca9084451a2f"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "7.7.1"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "24e6e11f1da131ed20b192d7d7b7ca9084451a2f"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "24e6e11f1da131ed20b192d7d7b7ca9084451a2f"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v7.7.1"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "7.7.1"
                      }
                    ],
                    "source": "DESCRIPTION"
                  }
                ]
              }
            }
          ],
          "versions": [
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            "v5.0.1",
            "v5.0.0",
            "v5.0.0-beta",
            "v4.13.0",
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            "v4.11.1",
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          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-77470.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:49.805172870Z",
      "provider": "osv",
      "references": [
        "https://github.com/LycheeOrg/Lychee/releases/tag/v7.7.1",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/77xxx/CVE-2026-77470.json",
        "https://github.com/LycheeOrg/Lychee/security/advisories/GHSA-476v-jr53-8rxc",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-77470",
        "https://github.com/LycheeOrg/Lychee/commit/24e6e11f1da131ed20b192d7d7b7ca9084451a2f",
        "https://github.com/LycheeOrg/Lychee/pull/4514"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-20",
          "CWE-472",
          "CWE-915"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/77xxx/CVE-2026-77470.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-77470",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 518450,
  "published_at": "2026-10-15T16:36:09.597+00:00"
}