CVE-2026-31821
CVE-2026-31821 is a CWE-862 vulnerability in sylius/sylius. O3 Security confirms whether CVE-2026-31821 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Sylius is Missing Authorization in API v2 Add Item Endpoint
Blast Radius
sylius/sylius🐘sylius/sylius🐘sylius/syliusReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Sylius is an Open Source eCommerce Framework on Symfony. The POST /api/v2/shop/orders/{tokenValue}/items endpoint does not verify cart ownership. An unauthenticated attacker can add items to other registered customers' carts by knowing the cart tokenValue. An attacker who obtains a cart tokenValue can add arbitrary items to another customer's cart. The endpoint returns the full cart representation in the response (HTTP 201). The issue is fixed in versions: 2.0.16, 2.1.12, 2.2.3 and above.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | sylius/sylius | ≥ 2.0.0&&< 2.0.16 | 2.0.16 |
| 🐘Packagist | sylius/sylius | ≥ 2.1.0&&< 2.1.12 | 2.1.12 |
| 🐘Packagist | sylius/sylius | ≥ 2.2.0&&< 2.2.3 | 2.2.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for sylius/sylius. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update sylius/sylius to 2.0.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-31821 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-31821 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-31821. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-31821 in your dependencies?
O3 detects CVE-2026-31821 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.