Arbitrary code execution via unchecked template evaluation
Published Apr 24, 2026 · Updated Apr 24, 2026
Deserialization in Ruby ERB allows attackers to execute arbitrary code when an application loads attacker-controlled Marshal data. ERB#def_method, ERB#def_module and ERB#def_class evaluate @src without the @_init check used by ERB#result and ERB#run. Exploitation requires untrusted data to reach Marshal.load while erb and ActiveSupport are loaded, after which code runs in the application process.
Summary
What happened
Deserialization in Ruby ERB allows attackers to execute arbitrary code when an application loads attacker-controlled Marshal data. ERB#def_method, ERB#def_module and ERB#def_class evaluate @src without the @_init check used by ERB#result and ERB#run. Exploitation requires untrusted data to reach Marshal.load while erb and ActiveSupport are loaded, after which code runs in the application process.
The record
- CVE
- CVE-2026-41316
- Published
- Apr 24, 2026
- Updated
- Apr 24, 2026
- Vendor
- libwww-perl
- Product
- ERB
- Classifications
- CWE-693, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 24, 2026CVE publishedPublication date reported by the CVE source.
- Apr 24, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 4.0.3.1
- Affected versionversion== 4.0.4
- Affected versionversion=>= 5.0.0, < 6.0.1.1
- Affected versionversion=>= 6.0.2, < 6.0.4
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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