Answer in brief
CVE-2020-11076 records a High severity (CVSS 7.5) vulnerability in HTTP Smuggling via Transfer-Encoding Header in Puma. The current sources do not mark it as known exploited. The current feed maps puma (rubygems), puma (rubygems). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps puma (rubygems), puma (rubygems). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| pumarubygems | >=0 <3.12.5 | 3.12.5 |
| pumarubygems | >=4.0.0 <4.3.4 | 4.3.4 |
Published upstream
May 22, 2020
Evidence: source:osv:source_dates:source-dates:recordSource modified
Sep 10, 2026
Evidence: source:osv:source_dates:source-dates:recordFirst seen by HOL
Aug 7, 2026
### Impact By using an invalid transfer-encoding header, an attacker could [smuggle an HTTP response.](https://portswigger.net/web-security/request-smuggling) Originally reported by @ZeddYu, who has our thanks for the detailed report. ### Patches The problem has been fixed in Puma 3.12.5 and Puma 4.3.4. ### For more information If you have any questions or comments about this advisory: * Open an issue in [Puma](https://github.com/puma/puma) * See our [security policy](https://github.com/puma/puma/security/policy)
Quoted source text, attributed separately from HOL analysis.