CVE-2026-41316 — erb
HIGHCVE-2026-41316 is a high-severity (CVSS 8.1) CWE-693 vulnerability in erb. A fix is available for erb — see the affected versions and patch details below.
ERB has an @_init deserialization guard bypass via def_module / def_method / def_class
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-41316.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-41316 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
erb💎erb💎erb💎erbReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | erb | all versions | 4.0.3.1bundle update erb --conservative |
| 💎RubyGems | erb | ≥ 4.0.4&&< 4.0.4.1 | 4.0.4.1bundle update erb --conservative |
| 💎RubyGems | erb | ≥ 5.0.0&&< 6.0.1.1 | 6.0.1.1bundle update erb --conservative |
| 💎RubyGems | erb | ≥ 6.0.2&&< 6.0.4 | 6.0.4bundle update erb --conservative |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for erb, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update erb to 4.0.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-41316 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-41316 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-41316. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 10 | ruby-0:3.3.10-12.el10_1 | RHSA-2026:18065 |
| Red Hat Enterprise Linux 10 | ruby4.0-0:4.0.3-34.el10_2 | RHSA-2026:20606 |
| Red Hat Enterprise Linux 10.0 Extended Update Support | ruby-0:3.3.10-11.el10_0.1 | RHSA-2026:33478 |
| Red Hat Enterprise Linux 8 | ruby:3.3-8100020260428163940.489197e6 | RHSA-2026:20614 |
| Red Hat Enterprise Linux 9 | ruby:3.3-9070020260428163621.9 | RHSA-2026:18030 |
| Red Hat Enterprise Linux 9 | ruby-0:3.0.7-166.el9_7 | RHSA-2026:18039 |
| Red Hat Enterprise Linux 9 | ruby:4.0-9080020260513131334.9 | RHSA-2026:20596 |
| Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions | ruby-0:3.0.4-160.2.el9_0 | RHSA-2026:20670 |
Frequently Asked Questions
Is CVE-2026-41316 in your dependencies?
O3 Security finds CVE-2026-41316 across RubyGems dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.