CVE-2026-77470

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

State: Published
Severity: 8.3 High
Published: Oct 15, 2026
Updated: Oct 15, 2026
Reserved: Aug 20, 2026

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Description

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.

Scores

CVSS	Score	Vector	Source
4.0	8.3 High	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	GitHub_M

Weaknesses

CWE-20 Improper Input Validation
CWE-472 External Control of Assumed-Immutable Web Parameter
CWE-915 Improperly Controlled Modification of Dynamically-Determined Object Attributes

Affected Products

Product	Versions
LycheeLycheeOrg	< 7.7.1Affected

References

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