{"id":"CVE-2026-41316","aliases":["GHSA-q339-8rmv-2mhv"],"url":"https://o3.security/vulnerability/CVE-2026-41316","summary":"ERB has an @_init deserialization guard bypass via def_module / def_method / def_class","details":"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.","published":"2026-04-24T02:35:41.160Z","modified":"2026-08-27T11:31:16.891148524Z","cvss":{"score":8.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":{"score":0.01131,"percentile":0.6354,"asOf":"2026-08-13"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"RubyGems","name":"erb","fixedVersion":"4.0.3.1"},{"ecosystem":"RubyGems","name":"erb","fixedVersion":"4.0.4.1"},{"ecosystem":"RubyGems","name":"erb","fixedVersion":"6.0.1.1"},{"ecosystem":"RubyGems","name":"erb","fixedVersion":"6.0.4"}],"fix":null,"references":[{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-41316.json"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:18030"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:18039"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:18065"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:20596"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:20606"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:20614"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:20670"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:26312"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:26655"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:33462"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:33478"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:35834"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:37238"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-41316"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/41xxx/CVE-2026-41316.json"},{"type":"ADVISORY","url":"https://github.com/ruby/erb/security/advisories/GHSA-q339-8rmv-2mhv"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-41316"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2461369"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-27T11:31:16.891148524Z"}}