CVE-2026-41316 (GCVE-0-2026-41316)

Vulnerability from cvelistv5 – Published: 2026-04-24 02:35 – Updated: 2026-04-25 01:45
VLAI
Title
ERB has an @_init deserialization guard bypass via def_module / def_method / def_class
Summary
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.
Severity
8.1 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
  • CWE-693 - Protection Mechanism Failure
Assigner
References
Impacted products
Vendor Product Version
ruby erb Affected: < 4.0.3.1
Affected: = 4.0.4
Affected: >= 5.0.0, < 6.0.1.1
Affected: >= 6.0.2, < 6.0.4
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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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