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CVE-2026-41316— ERB has an @_init deserialization guard bypass via def_module / def_method / def_class

Quick assessment

Affected
ruby erb
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.

ERB是The Ruby Programming Language开源的一款嵌入式Ruby模板处理工具。 ERB存在安全漏洞，该漏洞源于ERB#def_method、ERB#def_module和ERB#def_module方法未对@src进行保护，可能导致攻击者通过Marshal.load触发反序列化时，使用ERB#def_module作为代码执行点，绕过@_init保护。以下版本受到影响：ERB 4.0.3.1之前版本、4.0.4.1之前版本、6.0.1.1之前版本和6.0.4之前版本。

CVSS 8.1 · High EPSS 1.31% · P70

Affected Version Matrix 4

VendorProduct Version RangeStatus
ruby erb < 4.0.3.1 affected
= 4.0.4 affected
>= 5.0.0, < 6.0.1.1 affected
>= 6.0.2, < 6.0.4 affected
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I. Basic Information for CVE-2026-41316

Vulnerability Information
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Vulnerability Title
ERB has an @_init deserialization guard bypass via def_module / def_method / def_class
Source: CVE Program / CVE List V5
Vulnerability Description
ERB is a templating system for Ruby. Ruby 2.7.0 (before ERB 2.2.0 was published on rubygems.org) introduced an `@_init` instance variable guard in `ERB#result` and `ERB#run` to prevent code execution when an ERB object is reconstructed via `Marshal.load` (deserialization). However, three other public methods that also evaluate `@src` via `eval()` were not given the same guard: `ERB#def_method`, `ERB#def_module`, and `ERB#def_class`. An attacker who can trigger `Marshal.load` on untrusted data in a Ruby application that has `erb` loaded can use `ERB#def_module` (zero-arg, default parameters) as a code execution sink, bypassing the `@_init` protection entirely. ERB 4.0.3.1, 4.0.4.1, 6.0.1.1, and 6.0.4 patch the issue.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
保护机制失效
Source: CVE Program / CVE List V5
Vulnerability Title
ERB 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
ERB是The Ruby Programming Language开源的一款嵌入式Ruby模板处理工具。 ERB存在安全漏洞，该漏洞源于ERB#def_method、ERB#def_module和ERB#def_module方法未对@src进行保护，可能导致攻击者通过Marshal.load触发反序列化时，使用ERB#def_module作为代码执行点，绕过@_init保护。以下版本受到影响：ERB 4.0.3.1之前版本、4.0.4.1之前版本、6.0.1.1之前版本和6.0.4之前版本。
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
ruby erb < 4.0.3.1 -

II. Public POCs for CVE-2026-41316

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III. Intelligence Information for CVE-2026-41316

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IV. Related Vulnerabilities

Same vendor: ruby
Same weakness: CWE-693

V. Comments for CVE-2026-41316

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