CVE-2026-77999 (GCVE-0-2026-77999)

Vulnerability from cvelistv5 – Published: 2026-09-03 11:58 – Updated: 2026-09-03 12:40
VLAI
Title
Joomla Extension - j2commerce.com - Unauthenticated PayPal callback forgery leading to order confirmation fraud in J2Store 1.0.0-3.3.21, 4.0.0-4.0.21, 4.1.0-4.1.6
Summary
Joomla Extension - j2commerce.com - Unauthenticated PayPal callback forgery leading to order confirmation fraud in J2Store 1.0.0-3.3.21, 4.0.0-4.0.21, 4.1.0-4.1.6 - The PayPal IPN listener's signature check (`_validateIPN()`) accepted `UNVERIFIED` and any non-`INVALID` response as valid, made its verification request with `CURLOPT_SSL_VERIFYPEER` disabled, and stored its verdict in a field nothing downstream ever checked — so processing continued regardless of the outcome. Separately, the paid-amount comparison only ran when `mc_gross` was a positive number; omitting the field from the POST body (`floatval(null) == 0`) skipped the check entirely. Combined with a merchant-configured `receiver_email` and a sequential, enumerable order id read from the `custom` field, an anonymous POST was enough to move a pending order straight to `CONFIRMED` with no payment, or force another customer's pending order to `FAILED`. `paypalv2.php` performed no amount check under any circumstances.
Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-03 12:25 UTC
CWE
  • CWE-472 - External Control of Assumed-Immutable Web Parameter
  • CWE-602 - Client-Side Enforcement of Server-Side Security
Assigner
Joomla CNA under the mitre root
CNA scorecard C 73/100 over 344 records in the last 180 days details
References
URL Tags
https://www.j2commerce.com/ product
Impacted products
Vendor Product Version CPE status
j2commerce.com J2Store extension for Joomla Affected: 1.0.0-3.3.21
Affected: 4.0.0-4.0.21
Affected: 4.1.0-4.1.6
guessed Create a notification for this product.
Credits
Phil Taylor, mysites.guru
Show details on NVD website
To clipboard 

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