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TI-2026-86708 Aliases CVE-2026-123566GHSA-4qxq-46gj-rw38

CPU amplification in devalue via sparse arrays in uneval

Priority LOW 38CWE-400Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-400.

Summary

Sveltejs devalue before 5.9.3 contains a denial of service flaw in which sparse arrays passed to uneval are not handled efficiently, causing CPU amplification (CWE-400). An attacker who can influence sparse values passed to uneval forces synchronous work proportional to the declared array length, blocking the event loop.

Written with Claude Haiku 5.5 from the sources below · 2026-11-08

Description from the CNA

Sveltejs devalue before 5.9.3 contains a denial of service vulnerability that allows attackers to cause CPU amplification by supplying sparse arrays to uneval. Attackers who influence sparse values passed to uneval can force synchronous work proportional to the declared array length, blocking the event loop.

Why it matters now

EPSS 0.00343 28th percentileScored 2026-11-08
Fix Fixed devalue (sveltejs): 5.9.3

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
sveltejsdevaluebefore 5.9.35.9.3Patch availableCNA
  • devalue Vendorsveltejs Affected before 5.9.3 Fixed in 5.9.3 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:svelte:devalue:*:*:*:*:*:*:*:*——sveltejs
  • cpe:2.3:a:svelte:devalue:*:*:*:*:*:*:*:* Versions — — ·sveltejs

Remediation

Update devalue to version 5.9.3, which fixes the flaw.

Written with Claude Haiku 5.5 from the sources below · 2026-11-08

  • Fix · CNA devalue (sveltejs) Fixed in 5.9.3

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    sveltejs devalue 5.9.3

    6 records Highest priority Priority LOW 6 LOW

    Other records, highest priority first

    • TI-2026-86707 Quadratic expansion in devalue uneval enables denial of servicePriority LOW 38
    • TI-2026-86706 Memory exhaustion in Sveltejs devalue via uneval sparse arraysPriority LOW 38
    • TI-2026-86705 Validation bypass in Devalue parse allows memory exhaustionPriority LOW 38
    Show all 6 records →

Timeline

  1. 2026-11-08 Threatist record created from CVE-2026-123566
  2. 2026-11-08 Alias added: GHSA-4qxq-46gj-rw38
  3. 2026-11-09 Priority changed: MEDIUM → LOW

References

Advisory 1

  • TI-2023-13469 SvelteKit framework has Insufficient CSRF protection for CORS requests CVSS 3.1HIGH 8.8
  • TI-2023-13464 SvelteKit has Insufficient Cross-Site Request Forgery Protection CVSS 3.1HIGH 8.8
  • TI-2024-15660 Sending a GET or HEAD request with a body crashes SvelteKit CVSS 3.1HIGH 7.5
  • TI-2024-30159 Potential mXSS vulnerability due to improper HTML escaping in svelte CVSS 3.1MEDIUM 6.1
  • TI-2025-23466 SvelteKit allows XSS via tracked search_params CVSS 3.1MEDIUM 5.4
  • TI-2025-13940 Svelte 5.46.0 - Hydratable Key Script-Breakout XSS (SSR) CVSS 4.0MEDIUM 5.3
See all 50 →

Sources

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