How severe is CVE-2026-39365?

No CVSS score has been assigned to CVE-2026-39365 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-39365?

CVE-2026-39365 affects the following packages: vite (npm), vite (npm), vite (npm). Ecosystems affected: npm.

How do I fix CVE-2026-39365?

Update vite to 8.0.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-39365 is resolved across your whole dependency graph.

How do I detect CVE-2026-39365 in my npm dependencies?

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

How do I mitigate CVE-2026-39365 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-2026-39365?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-39365 can be triaged on real exposure rather than presence alone.

Is CVE-2026-39365 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-39365 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-2026-39365?

CVE-2026-39365 has an EPSS (Exploit Prediction Scoring System) score of 1.0%, placing it in the 61th 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-2026-39365?

CVE-2026-39365 is classified as Path Traversal (CWE-22). 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-2026-39365?

A Nuclei detection template exists for CVE-2026-39365, 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-2026-39365 published, and has it been updated?

CVE-2026-39365 was published on April 7, 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-2026-39365 — vite

Fix: vitejs/vite#22161

CVE-2026-39365 is a Path Traversal vulnerability in vite. A fix is available for vite — see the affected versions and patch details below.

Vite has a Path Traversal in Optimized Deps `.map` Handling

Also known asGHSA-4w7w-66w2-5vf9

Published

Apr 7, 2026

Updated

Aug 12, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

Exploitation data as of Sep 25, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-39365.

EPSS Exploitation Probability

via FIRST.org ↗

1.0%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs61th percentile — riskier than 61% 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

3 pkgs 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.

7Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

vitenpm

169.3Mdownloads / week

Description

Summary

Any files ending with .map even out side the project can be returned to the browser.

Impact

Only apps that match the following conditions are affected:

explicitly exposes the Vite dev server to the network (using --host or server.host config option)
have a sensitive content in files ending with .map and the path is predictable

Details

In Vite v7.3.1, the dev server’s handling of .map requests for optimized dependencies resolves file paths and calls readFile without restricting ../ segments in the URL. As a result, it is possible to bypass the server.fs.strict allow list and retrieve .map files located outside the project root, provided they can be parsed as valid source map JSON.

PoC

Create a minimal PoC sourcemap outside the project root

cat > /tmp/poc.map <<'EOF'
{"version":3,"file":"x.js","sources":[],"names":[],"mappings":""}
EOF

Start the Vite dev server (example)

pnpm -C playground/fs-serve dev --host 127.0.0.1 --port 18080

Confirm that direct /@fs access is blocked by strict (returns 403) <img width="4004" height="1038" alt="image" src="https://github.com/user-attachments/assets/15a859a8-1dc6-4105-8d58-80527c0dd9ab" />
Inject ../ segments under the optimized deps .map URL prefix to reach /tmp/poc.map <img width="2790" height="846" alt="image" src="https://github.com/user-attachments/assets/5d02957d-2e6a-4c45-9819-3f024e0e81f2" />

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`vite`	≥ 8.0.0&&< 8.0.5	8.0.5`npm install vite@8.0.5`
📦npm	`vite`	≥ 7.0.0&&< 7.3.2	7.3.2`npm install vite@7.3.2`
📦npm	`vite`	all versions	6.4.2`npm install vite@6.4.2`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vite, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update vite to 8.0.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-39365 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-2026-39365 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-39365. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

How to detect CVE-2026-39365

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

nuclei -id cve-2026-39365 -u https://target

Template: Vite Dev Server - Path Traversal in Optimized Deps .map Handling
Severity: medium
Impact: An attacker can trigger auto-generated sourcemap responses for files outside the project directory, leaking absolute filesystem paths and potentially reading .map files containing sensitive source code or configuration data.
Remediation: Upgrade Vite to version 8.0.5, 7.3.2, 6.4.2 or later.

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

Frequently Asked Questions

### Summary Any files ending with `.map` even out side the project can be returned to the browser. ### Impact Only apps that match the following conditions are affected: - explicitly exposes the Vite dev server to the network (using `--host` or [`server.host` config option](https://vitejs.dev/config/server-options.html#server-host)) - have a sensitive content in files ending with `.map` and the path is predictable ### Details In Vite v7.3.1, the dev server’s handling of `.map` requests for optimized dependencies resolves file paths and calls `readFile` without restricting `../` segments

O3 Security · Impact-Aware SCA

Is CVE-2026-39365 in your dependencies?

O3 Security finds CVE-2026-39365 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