How severe is CVE-2026-27121?

CVE-2026-27121 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2026-27121 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (9th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-27121?

CVE-2026-27121 affects Svelte. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-27121?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-27121 have an EU (EUVD) identifier?

Yes. CVE-2026-27121 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-7521.

When was CVE-2026-27121 published?

CVE-2026-27121 was published on 2026-02-20 and last updated on 2026-06-17.

CVE-2026-27121

CVE-2026-27121 is a medium-severity vulnerability in Svelte with a CVSS 3.x base score of 5.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Severity: Medium (CVSS 3.x base score 5.4)
CVSS v4: 5.1
EPSS exploit prediction: 0% (9th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-7521
Weakness: CWE-79
Affected product: Svelte
Published: 2026-02-20
Last modified: 2026-06-17

Description

svelte performance oriented web framework. Versions of svelte prior to 5.51.5 are vulnerable to cross-site scripting (XSS) during server-side rendering. When using spread syntax to render attributes from untrusted data, event handler properties are included in the rendered HTML output. If an application spreads user-controlled or external data as element attributes, an attacker can inject malicious event handlers that execute in victims' browsers. This vulnerability is fixed in 5.51.5.

Frequently asked questions

What is CVE-2026-27121?: svelte performance oriented web framework. Versions of svelte prior to 5.51.5 are vulnerable to cross-site scripting (XSS) during server-side rendering. When using spread syntax to render attributes from untrusted data, event handler properties are included in the rendered HTML output. If an application spreads user-controlled or external data as element attributes, an attacker can inject malicious event handlers that execute in victims' browsers. This vulnerability is fixed in 5.51.5.
How severe is CVE-2026-27121?: CVE-2026-27121 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-27121 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (9th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-27121?: CVE-2026-27121 affects Svelte. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-27121?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-27121 have an EU (EUVD) identifier?: Yes. CVE-2026-27121 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-7521.
When was CVE-2026-27121 published?: CVE-2026-27121 was published on 2026-02-20 and last updated on 2026-06-17.

References

https://github.com/sveltejs/svelte/security/advisories/GHSA-f7gr-6p89-r883

Affected products (1)

cpe:2.3:a:svelte:svelte:*:*:*:*:*:node.js:*:*

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