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CVE-2026-27601— Underscore.js has unlimited recursion in _.flatten and _.isEqual, potential for DoS attack

Quick assessment

Affected
jashkenas underscore
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.

Underscore.js是jashkenas个人开发者的一个轻量级的JavaScript实用工具库。 Underscore.js 1.13.8之前版本存在安全漏洞，该漏洞源于_.flatten和_.isEqual函数使用无深度限制的递归，可能导致攻击者通过触发堆栈溢出造成拒绝服务。

AI Predicted 7.5 Difficulty: Easy EPSS 1.03% · P62

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking
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I. Basic Information for CVE-2026-27601

Vulnerability Information
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Vulnerability Title
Underscore.js has unlimited recursion in _.flatten and _.isEqual, potential for DoS attack
Source: CVE Program / CVE List V5
Vulnerability Description
Underscore.js is a utility-belt library for JavaScript. Prior to 1.13.8, the _.flatten and _.isEqual functions use recursion without a depth limit. Under very specific conditions, detailed below, an attacker could exploit this in a Denial of Service (DoS) attack by triggering a stack overflow. Untrusted input must be used to create a recursive datastructure, for example using JSON.parse, with no enforced depth limit. The datastructure thus created must be passed to _.flatten or _.isEqual. In the case of _.flatten, the vulnerability can only be exploited if it is possible for a remote client to prepare a datastructure that consists of arrays at all levels AND if no finite depth limit is passed as the second argument to _.flatten. In the case of _.isEqual, the vulnerability can only be exploited if there exists a code path in which two distinct datastructures that were submitted by the same remote client are compared using _.isEqual. For example, if a client submits data that are stored in a database, and the same client can later submit another datastructure that is then compared to the data that were saved in the database previously, OR if a client submits a single request, but its data are parsed twice, creating two non-identical but equivalent datastructures that are then compared. Exceptions originating from the call to _.flatten or _.isEqual, as a result of a stack overflow, are not being caught. This vulnerability is fixed in 1.13.8.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
不加限制或调节的资源分配
Source: CVE Program / CVE List V5
Vulnerability Title
Underscore.js 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Underscore.js是jashkenas个人开发者的一个轻量级的JavaScript实用工具库。 Underscore.js 1.13.8之前版本存在安全漏洞，该漏洞源于_.flatten和_.isEqual函数使用无深度限制的递归，可能导致攻击者通过触发堆栈溢出造成拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
jashkenas underscore < 1.13.8 -

II. Public POCs for CVE-2026-27601

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III. Intelligence Information for CVE-2026-27601

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Patches & Fixes for CVE-2026-27601 (2)

Vendor Advisories for CVE-2026-27601 (1)

IV. Related Vulnerabilities

Same product: underscore
Same weakness: CWE-770

V. Comments for CVE-2026-27601

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