HTTP Smuggling via Transfer-Encoding Header in Puma

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

• CISA KEV Not listed.
• EPSS 0.029, the 86th percentile, on 7 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

1. 31 Oct 2026, 15:16 UTC First seen by agentprime
2. 31 Oct 2026, 15:16 UTC Confirmed by OSV

Sources

• GitHub Advisory Database: GHSA-w64w-qqph-5gxm
• OSV: GHSA-w64w-qqph-5gxm
• github.com/puma/puma/security/advisories/GHSA-w64w-qqph-5gxm
• nvd.nist.gov/vuln/detail/CVE-2020-11077
• github.com/puma/puma
• github.com/puma/puma/blob/master/History.md#434435-and-31253126--2020-05-22
• github.com/rubysec/ruby-advisory-db/blob/master/gems/puma/CVE-2020-11077.yml
• lists.debian.org/debian-lts-announce/2020/10/msg00009.html
• lists.fedoraproject.org/archives/list/[email protected]/message/SKIY5H67GJIGJL6SMFWFLUQQQR3EMVPR
• lists.opensuse.org/opensuse-security-announce/2020-07/msg00034.html
• lists.opensuse.org/opensuse-security-announce/2020-07/msg00038.html

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.