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TI-2026-86703 Aliases CVE-2026-123561GHSA-2fcf-p6fg-p2wf

Sveltejs devalue parse bypasses __proto__ rejection via property keys

Priority LOW 28CWE-1321Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
Present
Impact type
—
Confidentiality · integrity · availability
None · Low · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA.

Summary

The devalue package for Svelte before 5.9.3 allows malformed null-prototype object keys to bypass the __proto__ rejection in parse through property-key coercion. This is an incomplete fix for GHSA-mwv9-gp5h-frr4. An unauthenticated remote attacker can supply crafted payloads that create objects with a __proto__ own property, which by itself does not cause prototype pollution (CWE-1321).

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

Description from the CNA

devalue before 5.9.3 allows malformed null-prototype object keys to bypass parse's __proto__ rejection through property-key coercion, an incomplete fix for GHSA-mwv9-gp5h-frr4. Attackers can supply crafted payloads that yield objects with a __proto__ own property, which alone does not cause prototype pollution.

Why it matters now

EPSS 0.00249 16th 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

Upgrade devalue to version 5.9.3 or later, which fixes this issue.

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-2026-86707 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
    Show all 6 records →

Timeline

  1. 2026-11-08 Threatist record created from CVE-2026-123561
  2. 2026-11-08 Alias added: GHSA-2fcf-p6fg-p2wf
  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