CVE-2020-5247
No exploitation reported by the sources we read.
- Published2020-02-28
- WeaknessCWE-113 · CWE-74
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
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
dates in UTC- 2020-02-2817:15CVE publishedNVD
Observed activity
isMalicious corpus · updated 2026-10-23 21:37 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2020-5247?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2020-5247?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD · OSV| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 2.3 | ≤ 2.3.0 | no fix published | NVD |
| 2.4 | ≥ 2.4.0, ≤ 2.4.7 | no fix published | NVD |
| 2.5 | ≥ 2.5.0, ≤ 2.5.6 | no fix published | NVD |
| 2.6 | ≥ 2.6.0, ≤ 2.6.4 | no fix published | NVD |
| 2.7 | = 2.7.0 | no fix published | NVD |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 2.6 | ≥ 2.6.0, < 2.6.5 | 2.6.5 | OSV |
| 2.5 | ≥ 2.5.0, < 2.5.7 | 2.5.7 | OSV |
| 2.4 | ≥ 2.4.0, < 2.4.8 | 2.4.8 | OSV |
| 2.3 | < 2.3.1 | 2.3.1 | OSV |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 2.6 | ≥ 2.6.0, < 2.6.5 | 2.6.5 | OSV |
| 2.5 | ≥ 2.5.0, < 2.5.7 | 2.5.7 | OSV |
| 2.4 | ≥ 2.4.0, < 2.4.8 | 2.4.8 | OSV |
| 2.3 | < 2.3.1 | 2.3.1 | OSV |
4 more products in the sources.
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Fix
Advisories and patches
- github.comMitigation
- www.ruby-lang.orgVendor Advisory
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
Sources
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- Published
- 2020-02-28
- Last Modified
- 2026-06-17
- NVD status
- Modified
Frequently asked questions
What is CVE-2020-5247?
Is CVE-2020-5247 actively exploited?
What is the CVSS score for CVE-2020-5247?
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Related vulnerabilities
Same product first, then the same vendor advisory and the same publication week.