CVE-2020-11076
In Puma (RubyGem) before 4.3.4 and 3.12.5, an attacker could smuggle an HTTP response, by using an invalid transfer-encoding header.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (4.09%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
In Puma (RubyGem) before 4.3.4 and 3.12.5, an attacker could smuggle an HTTP response, by using an invalid transfer-encoding header. The problem has been fixed in Puma 3.12.5 and Puma 4.3.4.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- EPSS
- 4.09% probability · 91th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-444
- Affected
- puma/puma · fedoraproject/fedora · debian/debian linux
- Source
- security-advisories@github.com
EPSS 4.1% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00034.htmlMailing List, Third Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00038.htmlMailing List, Third Party Advisory
- https://github.com/puma/puma/blob/master/History.md#434435-and-31253126--2020-05-22Release Notes
- https://github.com/puma/puma/commit/f24d5521295a2152c286abb0a45a1e1e2bd275bdPatch
- https://github.com/puma/puma/security/advisories/GHSA-x7jg-6pwg-fx5hThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2020/10/msg00009.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SKIY5H67GJIGJL6SMFWFLUQQQR3EMVPR/
- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00034.htmlMailing List, Third Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00038.htmlMailing List, Third Party Advisory
- https://github.com/puma/puma/blob/master/History.md#434435-and-31253126--2020-05-22Release Notes
- https://github.com/puma/puma/commit/f24d5521295a2152c286abb0a45a1e1e2bd275bdPatch
- https://github.com/puma/puma/security/advisories/GHSA-x7jg-6pwg-fx5hThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2020/10/msg00009.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SKIY5H67GJIGJL6SMFWFLUQQQR3EMVPR/
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.