CVE-2026-25500 Rack's Stored XSS in Rack::Directory via javascript: filenames rendered into anchor href
Attackers can execute arbitrary JavaScript in victim browsers by placing files with javascript: names in directories served by Rack::Directory.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-25500?
CVE-2026-25500 is a medium-severity cross-site scripting vulnerability in rack, published on 18 Feb 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
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.
Weakness: CWE-79
Which versions are affected by CVE-2026-25500?
6 open source packages ship an affected version, including rack. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
rack RubyGems | All versions | 2.2.22 |
rack RubyGems | All versions | 2.2.22 |
rack RubyGems | From 3.0.0.beta1 | 3.1.20 |
rack RubyGems | From 3.0.0.beta1 | 3.1.20 |
rack RubyGems | From 3.2.0 | 3.2.5 |
rack RubyGems | From 3.2.0 | 3.2.5 |
Products include Rack Rack.
How do I fix CVE-2026-25500?
Upgrade rack to a fixed version for your release line: 2.2.22, 3.1.20 or 3.2.5.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-25500 being exploited?
There is no known exploitation of CVE-2026-25500 in the wild and no public exploit code.
Other vulnerabilities in rack
- CVE-2026-34785 Rack: Local file inclusion in `Rack::Static` via URL Prefix Matching
- CVE-2026-34827 Rack: Algorithmic-Complexity DoS in Rack::Multipart::Parser
- CVE-2026-34829 Rack: Denial of Service via Unbounded Multipart File Upload Without Content-Length
- CVE-2026-22860 Rack has a Directory Traversal via Rack:Directory
- CVE-2025-61919 Rack is vulnerable to a memory-exhaustion DoS through unbounded URL-encoded body parsing
Sources
Also known as CLEANSTART-2026-IX45302, CLEANSTART-2026-ZK59017, DEBIAN-CVE-2026-25500, GHSA-whrj-4476-wvmp, MINI-245w-r8vc-rxp3, MINI-285j-m8h2-77m4 and 21 more.