How severe is CVE-2026-27971?

No CVSS score has been assigned to CVE-2026-27971 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-27971?

CVE-2026-27971 affects the following packages: @builder.io/qwik (npm). Ecosystems affected: npm.

How do I fix CVE-2026-27971?

Update @builder.io/qwik to 1.19.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-27971 is resolved across your whole dependency graph.

How do I detect CVE-2026-27971 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @builder.io/qwik, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-27971 if there is no patch (or I can't update yet)?

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 does O3 Security protect against CVE-2026-27971?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-27971 can be triaged on real exposure rather than presence alone.

Is CVE-2026-27971 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-27971 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-27971?

CVE-2026-27971 has an EPSS (Exploit Prediction Scoring System) score of 5.4%, placing it in the 92th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-27971?

CVE-2026-27971 is classified as Deserialization of Untrusted Data (CWE-502). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

Is there exploit tooling available for CVE-2026-27971?

A Nuclei detection template exists for CVE-2026-27971, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2026-27971 published, and has it been updated?

CVE-2026-27971 was published on March 3, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

CVE-2026-27971 — qwik

CVE-2026-27971 is a Deserialization of Untrusted Data vulnerability in @builder.io/qwik. A fix is available for @builder.io/qwik — see the affected versions and patch details below.

Qwik affected by unauthenticated RCE via server$ Deserialization

Also known asGHSA-p9x5-jp3h-96mm

Published

Mar 3, 2026

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 18, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
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-2026-27971.

EPSS Exploitation Probability

via FIRST.org ↗

5.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs92th percentile — riskier than 92% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

1 pkg affected

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.

29other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

@builder.io/qwiknpm

43Kdownloads / week

Description

Qwik is a performance focused javascript framework. qwik <=1.19.0 is vulnerable to RCE due to an unsafe deserialization vulnerability in the server$ RPC mechanism that allows any unauthenticated user to execute arbitrary code on the server with a single HTTP request. Affects any deployment where require() is available at runtime. This vulnerability is fixed in 1.19.1.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@builder.io/qwik`	all versions	1.19.1`npm install @builder.io/qwik@1.19.1`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @builder.io/qwik, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @builder.io/qwik to 1.19.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-27971 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-27971 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-27971. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

How to detect CVE-2026-27971

A community-maintained Nuclei template exists for this CVE. You can scan for it directly:

nuclei -id cve-2026-27971 -u https://target

Template: Qwik - Unauthenticated RCE via server$ Deserialization
Severity: critical
Impact: Unauthenticated attackers can execute arbitrary code on the server, leading to full system compromise.
Remediation: Update to version 1.19.1 or later.

Template by ProjectDiscovery nuclei-templates (omarkurt), MIT licensed. View the full template. Scan only systems you are authorised to test.

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2026-27971 in your dependencies?

O3 Security finds CVE-2026-27971 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works