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TI-2026-21573 Aliases CVE-2026-27121GHSA-f7gr-6p89-r883

Svelte affected by cross-site scripting via spread attributes in Svelte SSR

Priority LOW 23CWE-79Published · Updated

Key facts

Attack vector
Network
Privileges required
High
User interaction
None
Attack complexity
High
Attack requirements
Present
Impact type
Cross-site scripting
Confidentiality · integrity · availability
Low · None · None
Fix status
Partial Red Hat: 1 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-79.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0022 12th percentileScored 2026-11-07
Fix Partial svelte (sveltejs): 5.51.5svelte (npm): 5.51.5Red Hat: 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
sveltejssveltebefore 5.51.55.51.5Patch availableCNA
—svelte (npm)before 5.51.55.51.5Patch availableGHSA-f7gr-6p89-r883
  • svelte Vendorsveltejs Affected before 5.51.5 Fixed in 5.51.5 Patch available CNA
  • svelte (npm) Vendor— Affected before 5.51.5 Fixed in 5.51.5 Patch available GHSA-f7gr-6p89-r883

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:svelte:svelte:*:*:*:*:*:node.js:*:*before 5.51.5Vulnerablesveltejs
  • cpe:2.3:a:svelte:svelte:*:*:*:*:*:node.js:*:* Versions before 5.51.5 Vulnerable ·sveltejs

Remediation

  • Fix · CNA svelte (sveltejs) Fixed in 5.51.5
  • Fix · GHSA-f7gr-6p89-r883 svelte (npm) Fixed in 5.51.5 Advisory →

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Build of Podman Desktop - Tech PreviewAffectedNo fix yet: Fix deferred

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-27121
  2. 2026-10-03 Alias added: GHSA-f7gr-6p89-r883

References

Advisory 2

Other 1

  • TI-2024-30159 Potential mXSS vulnerability due to improper HTML escaping in svelte CVSS 3.1MEDIUM 6.1
  • TI-2025-13940 Svelte 5.46.0 - Hydratable Key Script-Breakout XSS (SSR) CVSS 4.0MEDIUM 5.3
  • TI-2021-10070 The unofficial Svelte extension before 104.8.0 for Visual Studio Code allows attackers to… CVSS 3.1HIGH 7.8
  • TI-2022-09436 Cross-site scripting (XSS) in svelte CVSS 3.1MEDIUM 6.1
  • TI-2026-30847 Svelte: ReDoS in `<svelte:element>` Tag Validation CVSS 4.0MEDIUM 5.9
  • TI-2026-30853 Svelte: XSS via DOM Clobbering of Internal Framework State CVSS 4.0MEDIUM 5.3
See all 12 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences