CVE-2026-41316ERB has an @_init deserialization guard bypass via def_module / def_method / def_class
Updated under an hour ago ()
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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.
- CVSS
- 8.1 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-693, CWE-502
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Deferred
- Record last updated
- Aug 24, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
ruby erb ruby:erb (from the name) | before 4.0.3.1; = 4.0.4; from 5.0.0, < 6.0.1.1; from 6.0.2, < 6.0.4 | CNA record |
Red Hat Red Hat Enterprise Linux 10 redhat:enterprise_linux | from 0:3.3.10-12.el10_1 not affected | CISA ADP |
Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support redhat:enterprise_linux_eus | from 0:3.3.10-11.el10_0.1 not affected | CISA ADP |
from 0:3.0.4-160.2.el9_0 not affected | CISA ADP | |
Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support redhat:rhel_eus | from 0:3.0.7-165.el9_6.1 not affected | CISA ADP |
Red Hat Red Hat Hardened Images redhat:hummingbird | 1 | CISA ADP |
Red Hat Red Hat OpenShift Container Platform 4 redhat:openshift | 4 | CISA ADP |
References
- https://github.com/ruby/erb/security/advisories/GHSA-q339-8rmv-2mhvx-refsource-confirm
- https://access.redhat.com/errata/RHSA-2026:18030
- https://access.redhat.com/errata/RHSA-2026:18039
- https://access.redhat.com/errata/RHSA-2026:18065
- https://access.redhat.com/errata/RHSA-2026:20596
- https://access.redhat.com/errata/RHSA-2026:20606
- https://access.redhat.com/errata/RHSA-2026:20614
- https://access.redhat.com/errata/RHSA-2026:20670
- https://access.redhat.com/errata/RHSA-2026:26312
- https://access.redhat.com/errata/RHSA-2026:26655
- https://access.redhat.com/errata/RHSA-2026:33462
- https://access.redhat.com/errata/RHSA-2026:33478
- https://access.redhat.com/errata/RHSA-2026:35834
- https://access.redhat.com/errata/RHSA-2026:37238
- https://access.redhat.com/security/cve/CVE-2026-41316
- https://bugzilla.redhat.com/show_bug.cgi?id=2461369
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-41316.json
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.