CVE-2020-11076: HTTP Smuggling via Transfer-Encoding Header in Puma
Vulnerability summary
CVE-2020-11076 is a high (CVSS 7.5) vulnerability in debian debian_linux. EPSS estimates a 4.09% chance of exploitation in the next 30 days, higher than 90.7% of scored vulnerabilities.
Severe, CVSS 7.5 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 4% (FIRST, 03-11-2026)
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 23 · Related 22Timeline
- 22-05-2020PublishedVulnerability first disclosed.
- 04-08-2024Last modifiedVulnerability information updated.
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 metrics
6 scores · 5 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- OSV · RubygemsEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS trend
Probability
4.09%
Chance of exploitation in the next 30 days
Percentile
91%
Versus all other CVEs
30-day change
No change 0.00 pp
From 4.09% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Debian2 products
- puma< 4.3.6-1
- debian_linuxEOL9.0
Fedoraproject1 product
- fedoraEOL33
Puma1 product
- puma< 3.12.5 | ≥ 4.0.0, < 4.3.4 | ≥ 3.0.0, < 3.12.6 | ≥ 4.0.0, < 4.3.5
RubyGems1 product
- puma< 3.12.5 | ≥ 4.0.0, < 4.3.4
Ubuntu1 product
- puma< 3.12.4-1ubuntu2+esm1
5 vendors · 6 products
References
15 links- github.com/puma/puma/security/advisories/GHSA-x7jg-6pwg-fx5hX Refsource CONFIRMREPORTWEBThird Party Advisory
- lists.opensuse.org/opensuse-security-announce/2020-07/msg00034.htmlVendor AdvisoryX Refsource SUSEWEBMailing ListThird Party Advisory
- lists.opensuse.org/opensuse-security-announce/2020-07/msg00038.htmlVendor AdvisoryX Refsource SUSEWEBMailing ListThird Party Advisory
lists.debian.org/debian-lts-announce/2020/10/msg00009.htmlMailing ListX Refsource MLISTWEBThird Party Advisory
