CVE-2020-5247HTTP Response Splitting in Puma
- 6.5MediumCVSS base score
- 2.5%Exploitation in 30 daysEPSS · top 15% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
In Puma (RubyGem) before 4.3.2 and before 3.12.3, if an application using Puma allows untrusted input in a response header, an attacker can use newline characters (i.e. `CR`, `LF` or`/r`, `/n`) to end the header and inject malicious content, such as additional headers or an entirely new response body. This vulnerability is known as HTTP Response Splitting. While not an attack in itself, response splitting is a vector for several other attacks, such as cross-site scripting (XSS). This is related to CVE-2019-16254, which fixed this vulnerability for the WEBrick Ruby web server. This has been fixed in versions 4.3.2 and 3.12.3 by checking all headers for line endings and rejecting headers with those characters.
Timeline
ID reserved
By GitHub_M
- 57 days later
· 57 days later
Published
- 4 years later
· 4 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L |
| NVDNVD · Modified | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N |
- EPSS (exploitation in 30 days)
- 2.5% · top 15% of all CVEs (13 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- RubyGemspumaGHSA-84j7-475p-hp8v (opens in a new tab)
References
References7
- https://github.com/puma/puma/security/advisories/GHSA-84j7-475p-hp8v (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://owasp.org/www-community/attacks/HTTP_Response_Splitting (opens in a new tab)x_refsource_MISCx_transferred
- https://www.ruby-lang.org/en/news/2019/10/01/http-response-splitting-in-webrick-cve-2019-16254 (opens in a new tab)x_refsource_MISCx_transferred
- FEDORA-2020-a3f26a9387 (opens in a new tab)vendor-advisoryx_refsource_FEDORAx_transferred
- FEDORA-2020-fd87f90634 (opens in a new tab)vendor-advisoryx_refsource_FEDORAx_transferred
- FEDORA-2020-08092b4c97 (opens in a new tab)vendor-advisoryx_refsource_FEDORAx_transferred
- [debian-lts-announce] 20220525 [SECURITY] [DLA 3023-1] puma security update (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2020-0295 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-84j7-475p-hp8v (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2020-5247)Record last updated .