How severe is CVE-2026-27902?

No CVSS score has been assigned to CVE-2026-27902 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-27902?

CVE-2026-27902 affects the following packages: svelte (npm). Ecosystems affected: npm.

How do I fix CVE-2026-27902?

Update svelte to 5.53.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-27902 is resolved across your whole dependency graph.

How do I detect CVE-2026-27902 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-2026-27902 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-2026-27902 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-27902 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-2026-27902?

CVE-2026-27902 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 20th 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-2026-27902?

CVE-2026-27902 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-2026-27902 published, and has it been updated?

CVE-2026-27902 was published on February 26, 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-2026-27902 — svelte

Fix: sveltejs/svelte@0298e97

CVE-2026-27902 is a Cross-site Scripting (XSS) vulnerability in svelte. A fix is available for svelte — see the affected versions and patch details below.

Svelte Vulnerable to XSS via HTML Comment Injection in SSR Error Boundary Hydration Markers

Also known asGHSA-qgvg-pr8v-6rr3

Published

Feb 26, 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

No confirmed exploitation observed yet

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-2026-27902.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs20th percentile — riskier than 20% 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

Svelte performance oriented web framework. Prior to version 5.53.5, errors from transformError were not correctly escaped prior to being embedded in the HTML output, causing potential HTML injection and XSS if attacker-controlled content is returned from transformError. Version 5.53.5 fixes the issue.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`svelte`	≥ 5.53.0&&< 5.53.5	5.53.5`npm install svelte@5.53.5`

Affected Products

1 product · 1 configurations

Application

sveltesvelte

≥ 5.53.0 && < 5.53.5

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 5.53.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-27902 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.

Frequently Asked Questions

Svelte performance oriented web framework. Prior to version 5.53.5, errors from `transformError` were not correctly escaped prior to being embedded in the HTML output, causing potential HTML injection and XSS if attacker-controlled content is returned from `transformError`. Version 5.53.5 fixes the issue.

O3 Security · Impact-Aware SCA

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