How severe is CVE-2025-15265?

No CVSS score has been assigned to CVE-2025-15265 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-15265?

CVE-2025-15265 affects the following packages: svelte (npm). Ecosystems affected: npm.

How do I fix CVE-2025-15265?

Update svelte to 5.46.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-15265 is resolved across your whole dependency graph.

How do I detect CVE-2025-15265 in my npm dependencies?

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

How do I mitigate CVE-2025-15265 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2025-15265 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-15265 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-2025-15265?

CVE-2025-15265 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 28th 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-2025-15265?

CVE-2025-15265 is classified as Cross-site Scripting (XSS) (CWE-79). 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.

When was CVE-2025-15265 published, and has it been updated?

CVE-2025-15265 was published on January 15, 2026 and was last updated on October 28, 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-2025-15265 — svelte

Fix: sveltejs/svelte@ef81048

CVE-2025-15265 is a Cross-site Scripting (XSS) vulnerability in svelte. A fix is available for svelte — see the affected versions and patch details below.

Svelte 5.46.0 - Hydratable Key Script-Breakout XSS (SSR)

Also known asGHSA-6738-r8g5-qwp3

Published

Jan 15, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 6, 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.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-15265.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs28th percentile — riskier than 28% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

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.

2Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

sveltenpm

9.3Mdownloads / week

Description

Summary

An XSS vulnerability exists in Svelte 5.46.0-2 resulting from improper escaping of hydratable keys. If these keys incorporate untrusted user input, arbitrary JavaScript can be injected into server-rendered HTML.

Details

When using the hydratable function, the first argument is used as a key to uniquely identify the data, such that the value is not regenerated in the browser.

This key is embedded into a <script> block in the server-rendered <head> without escaping unsafe characters. A malicious key can break out of the script context and inject arbitrary JavaScript into the HTML response.

Impact

This is a cross-site scripting vulnerability affecting applications that have the experimental.async flag enabled and use hydratable with keys incorporating untrusted user input.

Impact: Arbitrary JS execution in the client’s browser.
Exploitability: Remote, single-request if key is attacker-controlled.
Typical Outcomes:
- Session/token theft
- DOM defacement
- CSRF bypass via injected JS
- Account takeover depending on cookie/session strategy

Affected applications should upgrade to a patched version immediately.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`svelte`	≥ 5.46.0&&< 5.46.4	5.46.4`npm install svelte@5.46.4`

Affected Products

1 product · 1 configurations

Application

sveltesvelte

≥ 5.46.0 && < 5.46.3

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for svelte, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update svelte to 5.46.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-15265 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

This vulnerability is rated Moderate for Red Hat products that incorporate Svelte versions 5.46.0 through 5.46.2 and utilize server-side rendering (SSR) with async hydration. Exploitation requires an attacker to control keys passed to hydratable components, leading to script injection and remote script execution in…

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

Source: Red Hat security advisory for CVE-2025-15265 (CC BY 4.0)

Frequently Asked Questions

## Summary An XSS vulnerability exists in Svelte 5.46.0-2 resulting from improper escaping of `hydratable` keys. If these keys incorporate untrusted user input, arbitrary JavaScript can be injected into server-rendered HTML. ## Details When using the [`hydratable`](https://svelte.dev/docs/svelte/hydratable) function, the first argument is used as a key to uniquely identify the data, such that the value is not regenerated in the browser. This key is embedded into a `<script>` block in the server-rendered `<head>` without escaping unsafe characters. A malicious key can break out of the scrip

O3 Security · Impact-Aware SCA

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