CVE-2026-123568— Sveltejs devalue before 5.6.3 Prototype Pollution via uneval Output

Quick assessment

Affected

sveltejs devalue

Exploitation

No confirmed in-the-wild exploitation; assess based on exposure

Recommended action

Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Sveltejs 的 devalue 库在 5.6.3 版本之前存在原型污染漏洞。攻击者可通过向函数提供不可信数据来篡改对象原型。当生成的代码随后被求值时，会创建具有被污染原型的对象，导致输出数据的结构与原始输入不一致。

CVSS 4.4 · Medium Updated Nov 08, 2026

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

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Vulnerability Information

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Vulnerability Title

Sveltejs devalue before 5.6.3 Prototype Pollution via uneval Output

Source: CVE Program / CVE List V5

Vulnerability Description

Sveltejs devalue before 5.6.3 contains a prototype pollution vulnerability that allows attackers to alter object prototypes by supplying untrusted data to uneval. When the generated code is later evaluated, it creates objects with polluted prototypes, producing output data whose shape differs from the original input.

Source: CVE Program / CVE List V5

CVSS Information

CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:L/I:L/A:N

Source: CVE Program / CVE List V5

Vulnerability Type

CWE-1321

Source: CVE Program / CVE List V5

Affected Products

Vendor	Product	Affected Versions	CPE	Subscribe
sveltejs	devalue	0 ~ 5.6.3	-

II. Public POCs for CVE-2026-123568

#	POC Description	Source Link	Shenlong Link

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III. Intelligence Information for CVE-2026-123568

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Other References for CVE-2026-123568 (2)

https://github.com/sveltejs/devalue/security/advisories/GHSA-8qm3-746x-r74r vendor-advisory
https://www.vulncheck.com/advisories/sveltejs-devalue-before-5.6.3-prototype-pollution-via-uneval-output third-party-advisory

https://www.cve.org/CVERecord?id=CVE-2026-123568

Same Patch Batch · sveltejs · 2026-11-08 · 9 CVEs total

CVE-2026-123564	7.5 HIGH	Sveltejs devalue before 5.9.3 Memory Exhaustion via uneval Sparse Arrays
CVE-2026-123566	7.5 HIGH	Devalue before 5.9.3 CPU Amplification Denial of Service via uneval
CVE-2026-123569	7.5 HIGH	Devalue before 5.6.3 Denial of Service via Sparse Array Serialization
CVE-2026-123563	7.5 HIGH	Devalue before 5.9.3 Typed-Array Allocation Validation Bypass via parse
CVE-2026-123562	7.5 HIGH	Devalue 5.8.0 before 5.9.3 Denial of Service via stringifyAsync Unhandled Rejection
CVE-2026-123565	7.5 HIGH	Devalue before 5.9.3 Quadratic Expansion Denial of Service via uneval
CVE-2026-123567	3.7 LOW	Sveltejs devalue before 5.6.4 Prototype Injection via parse and unflatten
CVE-2026-123561	3.7 LOW	Sveltejs devalue before 5.9.3 __proto__ Rejection Bypass via Property-Key Coercion

IV. Related Vulnerabilities

Same product: devalue

Same vendor: sveltejs

Same weakness: CWE-1321