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Rack CVE-2026-25500

MEDIUM
Cross-site Scripting (XSS) (CWE-79)
2026-02-18 security-advisories@github.com GHSA-whrj-4476-wvmp
Ruby Red Hat Rack Suse
5.4
CVSS 3.1 · GitHub Advisory
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Vulnerability Assessment

Weakness
CWE
CWE-79
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization Output encoding, context-aware escaping
MITRE ATT&CK

2 techniques across 2 tactics: Initial Access, Execution

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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Impact

CVSS 5.4 (MEDIUM). Attack vector: Network. Complexity: Low. Privileges required: Low. User interaction: Required. Public exploit/POC available.
Exploit ScenarioDerived

An attacker could exploit this vulnerability to compromise the affected system.
This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

Rack's Directory module fails to sanitize filenames when generating HTML directory listings, allowing attackers to craft files with javascript: scheme names that execute arbitrary code when clicked. Authenticated users or those with access to directories containing maliciously named files can trigger stored XSS attacks affecting other users viewing the directory index. Public exploit code exists for versions prior to 2.2.22, 3.1.20, and 3.2.5.

Earlier versions of this analysis (1)
v1 Mar 12, 2026 - 21:55 CVSS 5.4

Rack is a modular Ruby web server interface. Prior to versions 2.2.22, 3.1.20, and 3.2.5, Rack::Directory generates an HTML directory index where each file entry is rendered as a clickable link. [CVSS 5.4 MEDIUM]

RemediationAI

A vendor patch is available — apply it immediately. Implement output encoding and Content Security Policy headers. Restrict network access to the affected service where possible.

Affected Packages

rubygems rack fix: 2.2.22, 3.1.20, 3.2.5

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in rubygems

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

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Technical ContextAI · show details

Classified as CWE-79 (Cross-site Scripting (XSS)). Affects Rack. Rack is a modular Ruby web server interface. Prior to versions 2.2.22, 3.1.20, and 3.2.5, Rack::Directory generates an HTML directory index where each file entry is rendered as a clickable link. If a file exists on disk whose basename starts with the javascript: scheme (e.g. javascript:alert(1)), the generated index contains an anchor whose href is exactly javascript:alert(1). Clicking the entry executes JavaScript in the browser (demonstrated with alert(1)). Versions 2.2.22, 3.1.20,

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

GitHub Advisory PRIMARY 5.4 MEDIUM
AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
SUSE MEDIUM
Red Hat 5.4 MEDIUM

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

Lifecycle Timeline

3
PoC Detected
Feb 19, 2026 - 18:26 vuln.today
Public exploit code
Patch released
Feb 19, 2026 - 18:26 nvd
Patch available
CVE Published
Feb 18, 2026 - 20:18 nvd
MEDIUM 5.4

DescriptionGitHub Advisory

Rack is a modular Ruby web server interface. Prior to versions 2.2.22, 3.1.20, and 3.2.5, Rack::Directory generates an HTML directory index where each file entry is rendered as a clickable link. If a file exists on disk whose basename starts with the javascript: scheme (e.g. javascript:alert(1)), the generated index contains an anchor whose href is exactly javascript:alert(1). Clicking the entry executes JavaScript in the browser (demonstrated with alert(1)). Versions 2.2.22, 3.1.20, and 3.2.5 fix the issue.

Executive ViewAI

Why It Matters

Organizations using Rack should be aware of moderate risk from CVE-2026-25500, a cross-site scripting vulnerability rated CVSS 5.4. Attackers could inject scripts to steal sessions or perform actions as authenticated users. Proof-of-concept code is publicly available. A patch is available and should be applied during regular vulnerability management.

Business Impact: Low
Compensating Controls

Apply vendor patch. If patching is delayed: implement CSP headers, enable HttpOnly cookies, deploy WAF XSS rules.

Threat Intelligence Overview

EPSS Score
0.0%
Top 90% exploitable
Exploit
POC
Public exploit code exists
Data Quality
4 sources
Confidence: Medium
NVD CVE.org EPSS Vendor GitHub

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC Yes
EPSS 0.0%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
Poc
System Exposure· derived
Open
Automatable· derived
No
Human Impact
Low

Priority Score

47
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +27
PoC: +20
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Affected Products (CPE)GitHub Advisory

cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*

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Same weakness CWE-79 – Cross-site Scripting (XSS)

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Vendor StatusVendor

SUSE

Severity: Medium
Product Status
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise High Availability Extension 15 SP7 Fixed
SUSE Linux Enterprise High Availability Extension 15 SP7 Fixed
SUSE Linux Enterprise High Availability Extension 16.0 Fixed
SUSE Linux Enterprise High Availability Extension 16.1 Fixed

References

Advisories & patches
PATCH https://github.com/rack/rack/commit/f2f225f297b99fbee3d9f51255d41f601fc40aff

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