Svelte: ReDoS in `<svelte:element>` Tag Validation
Priority LOW 27CWE-1333Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- High
- User interaction
- None
- Attack complexity
- High
- Attack requirements
- Present
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 2 without a fix
Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-1333.
Summary
Svelte is a performance oriented web framework. From version 5.51.5 to before version 5.55.7, an internal regex in the Svelte runtime can take exponential time to test in <svelte:element this={tag}></svelte:element>. This issue has been patched in version 5.55.7.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00451 39th percentileScored 2026-11-07
Fix Partial svelte (sveltejs): 5.55.7svelte (npm): 5.55.7Red Hat: 2 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
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| sveltejs | svelte | 5.51.5 to before 5.55.7 | 5.55.7 | Patch available | CNA |
| — | svelte (npm) | 5.51.5 to before 5.55.7 | 5.55.7 | Patch available | GHSA-9rmh-mm8f-r9h6 |
- svelte Vendorsveltejs Affected 5.51.5 to before 5.55.7 Fixed in 5.55.7 Patch available CNA
- svelte (npm) Vendor— Affected 5.51.5 to before 5.55.7 Fixed in 5.55.7 Patch available GHSA-9rmh-mm8f-r9h6
Remediation
- Fix · CNA svelte (sveltejs) Fixed in 5.55.7
- Fix · GHSA-9rmh-mm8f-r9h6 svelte (npm) Fixed in 5.55.7 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Build of Podman Desktop | Affected | No fix yet: Fix deferred |
| Red Hat Build of Podman Desktop - Tech Preview | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-42567
- 2026-10-03 Alias added: GHSA-9rmh-mm8f-r9h6
References
More sveltejs Svelte vulnerabilities
- 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-2026-30853 Svelte: XSS via DOM Clobbering of Internal Framework State CVSS 4.0MEDIUM 5.3
- TI-2026-22246 Svelte Vulnerable to XSS via HTML Comment Injection in SSR Error Boundary Hydration Markers CVSS 4.0MEDIUM 5.3
Sources
- CVE-2026-42567 · CVE Program
- CVE-2026-42567 · NVD
- FIRST EPSS
- GHSA-9rmh-mm8f-r9h6 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-42567 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences