Rails has a possible XSS vulnerability in its Action Pack debug exceptions (CVE-2026-33167) | HOL Guard CVE

Medium · CVSS 6.1CVE-2026-33167GHSA-PGM4-439C-5JP6

Rails has a possible XSS vulnerability in its Action Pack debug exceptions

Answer in brief

CVE-2026-33167 records a Medium severity (CVSS 6.1) vulnerability in Rails has a possible XSS vulnerability in its Action Pack debug exceptions. The current sources do not mark it as known exploited. The current feed maps actionpack (rubygems). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Mar 23, 2026Updated Sep 10, 2026Source checked Sep 10, 2026First seen by HOL Aug 7, 2026Material review Sep 10, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.1
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 6.1. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps actionpack (rubygems). Check affected ranges and fixed versions before updating.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:a:rubyonrails:rails::::::::	Not reported	Not reported

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
actionpackrubygems	>=8.1.0 <8.1.2.1	8.1.2.1

Recommended response

Check inventory. Check lockfiles and deployed manifests for actionpack.
Review the reported fix. Update actionpack to 8.1.2.1 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Mar 23, 2026
Evidence: source:nvd:source_dates:source-dates:record
Source modified
Sep 10, 2026
Evidence: source:nvd:source_dates:source-dates:record
First seen by HOL
Aug 7, 2026

Sources and claim methodology

Upstream source description

### Impact The debug exceptions page does not properly escape exception messages. A carefully crafted exception message could inject arbitrary HTML and JavaScript into the page, leading to XSS. This affects applications with detailed exception pages enabled (`config.consider_all_requests_local = true`), which is the default in development. ### Releases The fixed releases are available at the normal locations. ### Credit This issue was responsibly reported by Hackerone researcher [fbettag](https://hackerone.com/fbettag).

Quoted source text, attributed separately from HOL analysis.