# CVE-2020-5249: HTTP Response Splitting (Early Hints) in Puma

Source: https://junglewise.ai/threats/cve-2020-5249-http-response-splitting-early-hints-in-puma  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2020-03-03  
License: CC BY 4.0 with a link back

CVE-2020-5249 · Severity: low · CVSS 3.1 · Published 2020-03-03

HTTP Response Splitting (Early Hints) in Puma

Technologies: [puma (RubyGems)](https://junglewise.ai/threats/technologies/puma). Vendors: [RubyGems](https://junglewise.ai/threats/vendors/rubygems).

## Quick answers

**Is CVE-2020-5249 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2020-5249 being exploited in the wild.

**How severe is CVE-2020-5249?** Low severity, with a CVSS score of 3.1, published 3 March 2020.

**Which products and versions are affected?** puma (RubyGems) ECOSYSTEM:introduced=0,fixed=3.12.4.

**Is there a fix for CVE-2020-5249?** Yes. puma (RubyGems): upgrade to 3.12.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2020-5249?** Check whether you run puma (RubyGems) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- puma (RubyGems): upgrade to 3.12.4 or later

  ```sh
  bundle update puma
  ```


## Affected products

- puma (RubyGems) ECOSYSTEM:introduced=0,fixed=3.12.4

## Identifiers

- CVE-2020-5249
- GHSA-33vf-4xgg-9r58

## Related threats

- [Puma source IP spoofing via PROXY protocol injection](https://junglewise.ai/threats/cve-2026-47737-puma-source-ip-spoofing-via-proxy-protocol-injection)
- [Puma uncontrolled resource consumption in PROXY protocol v1 parser](https://junglewise.ai/threats/cve-2026-47736-puma-uncontrolled-resource-consumption-in-proxy-protocol-v1)
- [Puma's header normalization allows for client to clobber proxy set headers](https://junglewise.ai/threats/cve-2024-45614-puma-s-header-normalization-allows-for-client-to-clobber-proxy)
- [Puma HTTP Request/Response Smuggling vulnerability](https://junglewise.ai/threats/cve-2024-21647-puma-http-request-response-smuggling-vulnerability)
- [Puma HTTP Request/Response Smuggling vulnerability](https://junglewise.ai/threats/cve-2023-40175-puma-http-request-response-smuggling-vulnerability)