CVE-2026-56831

Shopper: Negative discount values accepted and propagated through order calculation pipeline

MEDIUM
6.5
CVSS Score
Published: September 15, 2026 at 05:42 PM UTC
Updated: September 30, 2026 at 05:51 PM UTC
1 product affected across 1 vendorShopper

Using shopper by shopperlabs?

Get instant alerts when new vulnerabilities affect shopper - before attackers find them.

Real-time alertsTrack your software stackFree plan available
Severity
MEDIUM6.5
Exploit prediction
EPSS 0.4%
SSVC
PoC

Description

Shopper is a Headless e-commerce Admin Panel. Prior to 2.9.0, the /cpanel/discounts administrative interface accepts negative fixed_amount discount values, persists them in sh_discounts, and passes them through vendor/shopper/cart/src/Discounts/DiscountCalculator.php and vendor/shopper/cart/src/Pipelines/Calculate.php without enforcing a positive-value invariant. Because the calculation subtracts discountTotal from the subtotal, a negative discount increases the resulting order total instead of reducing it. Malformed discount records can therefore cause incorrect pricing and financial data integrity failures, although the advisory does not establish a customer-facing exploitation path. This issue is fixed in version 2.9.0.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 2.9.0
Affected range stops below 2.9.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.5MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
HIGH
Availability
NONE
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-20

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Free plan, no card