Instituto Nacional de ciberseguridad. Sección Incibe
Instituto Nacional de Ciberseguridad. Sección INCIBE-CERT

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CVE-2026-27122

Severity CVSS v4.0:
MEDIUM
Type:
CWE-79 Cross-Site Scripting (XSS)
Publication date:
20/02/2026
Last modified:
23/02/2026

Description

svelte performance oriented web framework. Prior to 5.51.5, when using in server-side rendering, the provided tag name is not validated or sanitized before being emitted into the HTML output. If the tag string contains unexpected characters, it can result in HTML injection in the SSR output. Client-side rendering is not affected. This vulnerability is fixed in 5.51.5.

Impact

Vector 4.0
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:L/VI:N/VA:N/SC:H/SI:H/SA:N CVSS v4.0 Severity and Metrics:

Base Score: 5.10 MEDIUM
Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:L/VI:N/VA:N/SC:H/SI:H/SA:N

Attack Vector (AV): Network
Attack Complexity (AC): High
Attack Requirements (AT): Present
Privileges Required (PR): High
User Interaction (UI): None
Confidentiality (VC): Low
Integrity (VI): None
Availability (VA): None
Confidentiality (SC): High
Integrity (SI): High
Availability (SA): None

Base Score 4.0
5.10
Severity 4.0
MEDIUM
Vector 3.x
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N CVSS v3.1 Severity and Metrics:

Base Score: 5.40 MEDIUM
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): Low
User Interaction (UI): Required
Scope (S): Changed
Confidentiality (C): Low
Integrity (I): Low
Availability (A): None

Base Score 3.x
5.40
Severity 3.x
MEDIUM

Vulnerable products and versions

CPE From Up to
cpe:2.3:a:svelte:svelte:*:*:*:*:*:node.js:*:* 5.51.5 (excluding)

To consult the complete list of CPE names with products and versions, see this page


References to Advisories, Solutions, and Tools