- 6.5MediumCVSS base score
- 1.6%Exploitation in 30 daysEPSS · top 24% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
In Puma (RubyGem) before 4.3.3 and 3.12.4, if an application using Puma allows untrusted input in an early-hints header, an attacker can use a carriage return character 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-2020-5247, which fixed this vulnerability but only for regular responses. This has been fixed in 4.3.3 and 3.12.4.
Timeline
ID reserved
By GitHub_M
- 2 months later
· 2 months 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 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N |
- EPSS (exploitation in 30 days)
- 1.6% · top 24% of all CVEs (11 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-33vf-4xgg-9r58 (opens in a new tab)
References
References7
- https://owasp.org/www-community/attacks/HTTP_Response_Splitting (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/puma/puma/security/advisories/GHSA-33vf-4xgg-9r58 (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://github.com/puma/puma/security/advisories/GHSA-84j7-475p-hp8v (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/puma/puma/commit/c22712fc93284a45a93f9ad7023888f3a65524f3 (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
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-2020-0325 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-33vf-4xgg-9r58 (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-2020-5249)Record last updated .