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Fencer Intel
high 7.5

CVE-2020-11076 json

HTTP Smuggling via Transfer-Encoding Header in Puma

published 6y ago modified last mo. also GHSA-x7jg-6pwg-fx5h , EUVD-2020-0447

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
4.1%
EPSS 4.1% chance of exploitation in 30 days, percentile 90%
public exploits
0
none known

Summary

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.

Patch / fix

  • rubygems puma 3.12.5, 4.3.4
  • puma puma 3.12.6, 4.3.5
  • puma Debian 14, Debian 13, Debian 12 4.3.6-1

debian advisories DEBIAN-CVE-2020-11076

  • puma Ubuntu Pro 20.04 LTS 3.12.4-1ubuntu2+esm1

ubuntu advisories UBUNTU-CVE-2020-11076

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • rmt-server SLE Module for Server Applications 15 SP1, SLE Module for Public Cloud 15 SP1 2.6.5-3.18.1
  • rmt-server SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 2.6.5-3.34.1
  • rmt-server SLE Module for Server Applications 15 SP2, SLE Module for Public Cloud 15 SP2 2.6.5-3.3.1
  • kibana OpenStack Cloud 7 4.6.3-5.1
  • ansible OpenStack Cloud 7 2.2.3.0-12.2
  • grafana OpenStack Cloud 7 4.6.5-1.14.1
  • memcached OpenStack Cloud 7 1.5.17-3.6.1
  • python-py OpenStack Cloud 7 1.8.1-11.12.1

suse advisories SUSE-SU-2020:3160-1SUSE-SU-2020:3147-1SUSE-SU-2020:3036-1SUSE-RU-2020:2072-1SUSE-SU-2020:2060-1SUSE-SU-2020:1919-1

  • rubygem-puma openSUSE Tumbleweed 6.4.3-1.5
  • rubygem-puma openSUSE Tumbleweed 6.4.3-1.3
  • rmt-server openSUSE Tumbleweed 2.6.13-1.1
  • rubygem-puma-4 openSUSE Tumbleweed 4.3.10-1.1
  • rubygem-puma openSUSE Tumbleweed 5.6.2-1.1
  • rubygem-puma-5 openSUSE Tumbleweed 5.6.5-1.1
  • ruby3.2-rubygem-puma openSUSE Tumbleweed 6.0.0-2.1
  • ruby3.2-rubygem-puma-5 openSUSE Tumbleweed 5.6.5-1.7

opensuse advisories openSUSE-SU-2026:10357-1openSUSE-SU-2025:15123-1openSUSE-SU-2024:10589-1openSUSE-SU-2024:11830-1openSUSE-SU-2024:11847-1openSUSE-SU-2024:12592-1

Is CVE-2020-11076 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-11076 updated cvss 0.0

rubygem-puma: HTTP Smuggling via an invalid Transfer-Encoding Header

  • Red Hat CloudForms Management Engine 5 rubygem-puma Red Hat Storage 3 rubygem-puma
    affected: workaround, no fix planned “Will not fix”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

4.09% chance of exploitation in the next 30 days, higher than 90% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:P/A:N
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected packages

ecosystem package affected fixed in
rubygems puma
<3.12.5
>=4.0.0, <4.3.4
3.12.5
4.3.4

Affected products

  • puma puma

Classification

Weakness
  • CWE-444 Inconsistent Interpretation of HTTP Requests

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.