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TI-2026-86707 Aliases CVE-2026-123565GHSA-m5fj-453c-wwq4

Quadratic expansion in devalue uneval enables denial of service

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 resource exhaustion flaw in its uneval function. Repeated primitive strings cause quadratic expansion (CWE-400), so an unauthenticated remote attacker can send a small crafted payload that produces a very large serialized string, exhausting memory or CPU.

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 resource exhaustion vulnerability where repeated primitive strings cause quadratic expansion in the uneval function. Attackers can supply a small crafted payload that is parsed and then passed to uneval, producing a very large serialized string that exhausts memory or CPU.

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-2026-86708 CPU amplification in devalue via sparse arrays in unevalPriority 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-2026-123565
  2. 2026-11-08 Alias added: GHSA-m5fj-453c-wwq4
  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