CVE-2026-25150 is a critical-severity (CVSS 9.3) CWE-1321 vulnerability in @builder.io/qwik-city. A fix is available for @builder.io/qwik-city — see the affected versions and patch details below.
Prototype Pollution via FormData Processing in Qwik City
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-25150.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@builder.io/qwik-citynpmDescription
Summary
A Prototype Pollution vulnerability exists in the formToObj() function within @builder.io/qwik-city middleware. The function processes form field names with dot notation (e.g., user.name) to create nested objects, but fails to sanitize dangerous property names like __proto__, constructor, and prototype. This allows unauthenticated attackers to pollute Object.prototype by sending crafted HTTP POST requests, potentially leading to privilege escalation, authentication bypass, or denial of service.
Impact
An unauthenticated attacker can supply specially crafted form field names that cause formToObj() to write dangerous keys (for example proto, constructor, prototype) into parsed objects. This results in Prototype Pollution of the server process and can cause privilege escalation, auth bypass, denial-of-service, or other global application integrity failures depending on how objects are used.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @builder.io/qwik-city | all versions | 1.19.0npm install @builder.io/qwik-city@1.19.0 |
Affected Products
qwikqwikDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @builder.io/qwik-city, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @builder.io/qwik-city to 1.19.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-25150 is resolved across your whole dependency graph.
Workarounds
Close the privilege gap rather than the entry point: audit which accounts, roles and service identities can reach the affected operation, drop the component to the least privilege it actually needs, and review file and directory permissions created by earlier installs — a default left in place is what makes this reachable.
Frequently Asked Questions
Is CVE-2026-25150 in your dependencies?
Find it across npm, including transitive dependencies.