Cross-site scripting via lost SafeBuffer unsafe flag
Published Mar 23, 2026 · Updated Mar 23, 2026
Cross-site scripting in Rails Active Support before 7.2.3.1, 8.0.4.1, and 8.1.2.1 allows remote attackers to inject script. SafeBuffer#% creates a new buffer without copying the source buffer's html_unsafe state, so a mutated buffer is incorrectly treated as safe and bypasses ERB escaping. Exploitation requires an application to mutate the buffer in place, format it with untrusted arguments, and render the result, which executes script in a victim's browser.
Summary
What happened
Cross-site scripting in Rails Active Support before 7.2.3.1, 8.0.4.1, and 8.1.2.1 allows remote attackers to inject script. SafeBuffer#% creates a new buffer without copying the source buffer's html_unsafe state, so a mutated buffer is incorrectly treated as safe and bypasses ERB escaping. Exploitation requires an application to mutate the buffer in place, format it with untrusted arguments, and render the result, which executes script in a victim's browser.
The record
- CVE
- CVE-2026-33170
- Published
- Mar 23, 2026
- Updated
- Mar 23, 2026
- Vendor
- Rails
- Product
- Active Support
- Classifications
- CWE-79
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 23, 2026CVE publishedPublication date reported by the CVE source.
- Mar 23, 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=< 7.2.3.1
- Affected versionversion=>= 8.0.0.beta1, < 8.0.4.1
- Affected versionversion=>= 8.1.0.beta1, < 8.1.2.1
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
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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