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CVE-2026-123565— Devalue before 5.9.3 Quadratic Expansion Denial of Service via uneval

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 5.9.3 版本之前存在资源耗尽漏洞：当重复出现原始字符串时， 函数会产生二次级膨胀。攻击者可提供一个精心构造的小型载荷，该载荷被解析后传递给 ，从而生成一个极大的序列化字符串，导致内存或 CPU 资源耗尽。

CVSS 7.5 · High

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-123565

Vulnerability Information
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Vulnerability Title
Devalue before 5.9.3 Quadratic Expansion Denial of Service via uneval
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
sveltejs devalue 0 ~ 5.9.3 -

II. Public POCs for CVE-2026-123565

# POC Description Source Link Shenlong Link
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III. Intelligence Information for CVE-2026-123565

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Other References for CVE-2026-123565 (2)

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-2026-123568 4.4 MEDIUM Sveltejs devalue before 5.6.3 Prototype Pollution via uneval Output
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-400