CVE-2026-33167Network attack vector

Cross-site scripting via raw exception-message rendering

Published Mar 23, 2026 · Updated Mar 23, 2026

Cross-site scripting in Rails Action Pack 8.1.0 through 8.1.2 allows remote attackers to execute script via a crafted exception message. The debug exception layout inserts the message into a text/plain script element with raw ERB output, so a closing script tag escapes the container. Reachability requires detailed exception pages, enabled by consider_all_requests_local and default in development, plus a developer opening the crafted URL; the script can read or alter data accessible to that page.

CVSS severityUnavailable
Unscored
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Cross-site scripting in Rails Action Pack 8.1.0 through 8.1.2 allows remote attackers to execute script via a crafted exception message. The debug exception layout inserts the message into a text/plain script element with raw ERB output, so a closing script tag escapes the container. Reachability requires detailed exception pages, enabled by consider_all_requests_local and default in development, plus a developer opening the crafted URL; the script can read or alter data accessible to that page.

The record

CVE
CVE-2026-33167
Published
Mar 23, 2026
Updated
Mar 23, 2026
Vendor
Rails
Product
Action Pack
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 23, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 23, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 8.1.0, < 8.1.2.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Rails · Action Packversion=>= 8.1.0, < 8.1.2.1

Published CVSS scores

1.3GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo