What is the CVSS score of CVE-2026-27122?

CVE-2026-27122 has a CVSS 3.1 base score of 5.4 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N. EPSS exploitation probability: 0.0%.

Which versions of Svelte are affected by CVE-2026-27122?

CVE-2026-27122 presents moderate security risk, a cross-site scripting vulnerability rated CVSS 5.4. Attackers could inject scripts to steal sessions or perform actions as authenticated users.. A patch is available.

How to fix or mitigate CVE-2026-27122?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Verify Content-Security-Policy and output encoding.

Svelte CVE-2026-27122

MEDIUM

Cross-site Scripting (XSS) (CWE-79)

2026-02-20 security-advisories@github.com

GHSA-m56q-vw4c-c2cp

XSS Red Hat Svelte

5.4

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

5.4 MEDIUM

AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Red Hat

5.6 MEDIUM

qualitative

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Lifecycle Timeline

Patch released

Mar 31, 2026 - 21:13 nvd

Patch available

Analysis Generated

Mar 12, 2026 - 22:04 vuln.today

CVE Published

Feb 20, 2026 - 23:16 nvd

MEDIUM 5.4

Blast Radius

ecosystem impact

† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth

1 npm packages depend on svelte (1 direct, 0 indirect)

Ecosystem-wide dependent count for version 5.51.5.

DescriptionGitHub Advisory

svelte performance oriented web framework. Prior to 5.51.5, when using <svelte:element this={tag}> 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.

AnalysisAI

HTML injection in Svelte's server-side rendering occurs when the <svelte:element> tag parameter fails to sanitize user-supplied tag names, allowing attackers to inject malicious HTML into rendered output. This affects Svelte versions prior to 5.51.5 and requires user interaction to exploit, with client-side rendering remaining unaffected. An authenticated attacker can achieve limited information disclosure or modify page content for affected users.

Technical ContextAI

Classified as CWE-79 (Cross-site Scripting (XSS)). Affects Svelte. svelte performance oriented web framework. Prior to 5.51.5, when using <svelte:element this={tag}> 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.

RemediationAI

Fixed in version 5.51.5.. Implement output encoding and Content Security Policy headers. Restrict network access to the affected service where possible.