CVE-2026-100872 Sylius CVE debrief

Who should care

Defenders responsible for Sylius instances, e-commerce security teams, and payment gateway administrators should be aware of this vulnerability and take necessary actions to prevent exploitation.

Why it matters

CVE-2026-100872 is a high-severity vulnerability in Sylius that allows attackers to modify order totals after gateway transaction initiation, potentially leading to financial losses and reputational damage. Defenders should prioritize verifying and patching vulnerable instances to prevent exploitation.

• Potential financial losses due to modified order totals.
• Compromised order integrity and authenticity.
• Possible reputational damage due to security incident.
• Verification of Sylius instance vulnerability and patching.

Technical summary

Sylius versions before 2.1.16 and 2.2.9 fail to validate payment amounts during cart recalculation, allowing unauthenticated attackers to modify order totals after gateway transaction initiation. This vulnerability affects Sylius instances, potentially leading to financial losses and reputational damage. Defenders should prioritize verifying and patching vulnerable instances to prevent exploitation. The vulnerability is caused by a lack of validation of payment amounts during cart recalculation in Sylius, allowing attackers to pay a small amount, enlarge the order after gateway capture, and have the system mark the inflated order as fully paid while the gateway captured only the original amount.

Defensive priority

Defenders should prioritize verifying and patching vulnerable Sylius instances to prevent potential financial losses.

Recommended defensive actions

• Verify and patch vulnerable Sylius instances to prevent potential financial losses.
• Monitor for suspicious activity on Sylius instances, such as unusual order modifications or payments.
• Implement additional security measures, such as payment gateway validation and order verification, to prevent exploitation.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.

Evidence notes

The vulnerability is caused by a lack of validation of payment amounts during cart recalculation in Sylius. This allows attackers to modify order totals after gateway transaction initiation. The vulnerability affects Sylius versions before 2.1.16 and 2.2.9. Evidence is limited to public statements from the vendor and CVE Program record. Defenders should verify Sylius instance vulnerability and patching with explicit evidence limits.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.