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Full vulnerability report · 2026
CVE-2026-41316High confidence

ERB has an @_init deserialization guard bypass via def_module / def_method / def_class

ruby · erb

8.1HighCVSS 3.1
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
Distribution package intelligence

Ubuntu vendor package status

Canonical’s release and source-package findings are shown separately from local repository availability.

2 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Ubuntu releaseSource packageVendor stateFixed versionEvidence
Ubuntu 24.04 LTSnoble · standard archivejrubyUnder evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical record ↗Source updated 8 Sept 2026
Ubuntu 24.04 LTSnoble · standard archiveruby3.2Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical record ↗Source updated 8 Sept 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2026-41316 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityerb: ERB: Arbitrary code execution via deserialization bypass
1,349 fixed

The vendor explicitly identifies these products or versions as containing the fix.

  • ruby-0:3.3.10-11.el10_0.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)
  • ruby-0:3.3.10-11.el10_0.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)
  • ruby-0:3.3.10-11.el10_0.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)
  • ruby-0:3.3.10-11.el10_0.1.src as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)
  • ruby-0:3.3.10-11.el10_0.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)
  • ruby-bundled-gems-0:3.3.10-11.el10_0.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)
  • ruby-bundled-gems-0:3.3.10-11.el10_0.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)
  • ruby-bundled-gems-0:3.3.10-11.el10_0.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)
  • ruby-bundled-gems-0:3.3.10-11.el10_0.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)
  • ruby-bundled-gems-debuginfo-0:3.3.10-11.el10_0.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)
  • ruby-bundled-gems-debuginfo-0:3.3.10-11.el10_0.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)
  • ruby-bundled-gems-debuginfo-0:3.3.10-11.el10_0.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)
Summary
A flaw was found in ERB, a templating system for Ruby. An attacker who can trigger deserialization of untrusted data in a Ruby application can bypass existing protections. This vulnerability allows for arbitrary code execution by exploiting specific public methods that evaluate template source code, which were not properly guarded against deserialization attacks.
Remediation
For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-25385

No EUVD known-exploited evidence

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.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
8.1 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

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.

What

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.

Why

The product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

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.

Why

The product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Protection Mechanism Failure → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
High: exploitation depends on specific conditions
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-693 ↗

CWE-693: Protection Mechanism Failure. The product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedCWE-693
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-25385Official EUVD mapping

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.

Official EUVD record
BSI · German · WID-SEC-W-2026-2455Oracle Solaris Drittanbieterkomponenten: Mehrere Schwachstellen

Ein entfernter, anonymer oder authentisierter Angreifer kann mehrere Schwachstellen in verschiedenen Komponenten von Drittanbietern in Oracle Solaris ausnutzen, um einen nicht näher spezifizierten Angriff durchzuführen.

Official advisory
BSI · German · WID-SEC-W-2026-2379Ruby: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Ruby ausnutzen, um Informationen offenzulegen, um einen Denial of Service Angriff durchzuführen, und um beliebigen Programmcode auszuführen.

Official advisory
BSI · German · WID-SEC-W-2026-1187Ruby und Ruby on Rails (erb gem): Schwachstelle ermöglicht Codeausführung

Ein entfernter, anonymer Angreifer kann eine Schwachstelle in Ruby und Ruby on Rails ausnutzen, um Sicherheitsmaßnahmen zu umgehen und so beliebigen Code auszuführen.

Official advisory
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
< 4.0.3.1; = 4.0.4; >= 5.0.0, < 6.0.1.1; >= 6.0.2, < 6.0.4
Fixed
ruby-0:3.3.10-11.el10_0.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-0:3.3.10-11.el10_0.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-0:3.3.10-11.el10_0.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-0:3.3.10-11.el10_0.1.src as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-0:3.3.10-11.el10_0.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-bundled-gems-0:3.3.10-11.el10_0.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-bundled-gems-0:3.3.10-11.el10_0.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-bundled-gems-0:3.3.10-11.el10_0.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-bundled-gems-0:3.3.10-11.el10_0.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-bundled-gems-debuginfo-0:3.3.10-11.el10_0.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-bundled-gems-debuginfo-0:3.3.10-11.el10_0.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-bundled-gems-debuginfo-0:3.3.10-11.el10_0.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-bundled-gems-debuginfo-0:3.3.10-11.el10_0.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-debuginfo-0:3.3.10-11.el10_0.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-debuginfo-0:3.3.10-11.el10_0.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-debuginfo-0:3.3.10-11.el10_0.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-debuginfo-0:3.3.10-11.el10_0.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-debugsource-0:3.3.10-11.el10_0.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-debugsource-0:3.3.10-11.el10_0.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-debugsource-0:3.3.10-11.el10_0.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-debugsource-0:3.3.10-11.el10_0.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-default-gems-0:3.3.10-11.el10_0.1.noarch as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-devel-0:3.3.10-11.el10_0.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-devel-0:3.3.10-11.el10_0.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-devel-0:3.3.10-11.el10_0.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-devel-0:3.3.10-11.el10_0.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-libs-0:3.3.10-11.el10_0.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-libs-0:3.3.10-11.el10_0.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-libs-0:3.3.10-11.el10_0.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); ruby-libs-0:3.3.10-11.el10_0.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0); and 1319 more
Action
For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 24 Apr 2026 · Last source change 24 Aug 2026, 12:06 UTC · CWE-693 · Protection Mechanism Failure

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-25385
Product sourceCNA
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD not scheduled

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates →

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
ENISA EUVD · EUVD-2026-25385↗Vendor CSAF · Red Hat Product Security↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-41316 · cve.blacktree.nl