CVE-2020-11076 [High] | Security Vulnerability in Puma

CVE-2020-11076 is rated Moderate Risk (58.8/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.78%). Review affected assets and schedule remediation.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-04-07	1.94%	1.78%	-0.16%
2	2026-03-25	1.78%	1.94%	+0.16%
3	2026-03-04	—	1.78%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-04-07

1.94%

1.78%

-0.16%

2026-03-25

1.78%

1.94%

+0.16%

2026-03-04

—

1.78%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.5	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:N) Service keeps running; no real outage angle.	3.9	3.6	[email protected]
7.5	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:N) Service keeps running; no real outage angle.	3.9	3.6	[email protected]
5.0	2.0	MEDIUM	`AV:N/AC:L/Au:N/C:N/I:P/A:N` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:N) No authentication is required. Confidentiality impact (C:N) No confidentiality impact. Integrity impact (I:P) Partial integrity impact. Availability impact (A:N) No availability impact.	10.0	2.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.5

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N): Service keeps running; no real outage angle.

3.9

3.6

[email protected]

7.5

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N): Service keeps running; no real outage angle.

3.9

3.6

[email protected]

5.0

2.0

MEDIUM

AV:N/AC:L/Au:N/C:N/I:P/A:N Click to expand

Access vector (AV:N): Can be exploited remotely over network reachability.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:N): No confidentiality impact.
Integrity impact (I:P): Partial integrity impact.
Availability impact (A:N): No availability impact.

10.0

2.9

[email protected]

OS Trackers for CVE-2020-11076

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2020-11076 not yet assigned priority: Debian including 1 source packages (puma), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5.	https://security-tracker.debian.org/tracker/CVE-2020-11076
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2020-11076
`suse`	medium	—	https://www.suse.com/security/cve/CVE-2020-11076/
`ubuntu`	medium	CVE-2020-11076 medium priority: Ubuntu including 1 source packages (puma), 16 status rows across 16 suites (bionic, eoan, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, trusty, upstream, xenial): not-affected 7, ignored 4, DNE 3, needs-triage 1, released 1.	https://ubuntu.com/security/CVE-2020-11076

Affected software / configurations for CVE-2020-11076

Vendor	Product	Version	Raw CPE
puma	puma	>= 3.0.0, < 3.12.6	cpe:2.3:a:puma:puma::::::ruby::*
puma	puma	>= 4.0.0, < 4.3.5	cpe:2.3:a:puma:puma::::::ruby::*
fedoraproject	fedora	33	cpe:2.3:o:fedoraproject:fedora:33:::::::*
debian	debian_linux	9.0	cpe:2.3:o:debian:debian_linux:9.0:::::::*

References for CVE-2020-11076

URL	Tags
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00034.html	Mailing List Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00038.html	Mailing List Third Party Advisory
https://github.com/puma/puma/blob/master/History.md#434435-and-31253126--2020-05-22	Release Notes
https://github.com/puma/puma/commit/f24d5521295a2152c286abb0a45a1e1e2bd275bd	Patch
https://github.com/puma/puma/security/advisories/GHSA-x7jg-6pwg-fx5h	Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/10/msg00009.html	Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SKIY5H67GJIGJL6SMFWFLUQQQR3EMVPR/

URL

CVE-2020-11076 | HTTP Smuggling via Transfer-Encoding Header in Puma

Exploit prediction scoring system (EPSS) score for CVE-2020-11076

Common vulnerability scoring system (CVSS) metrics for CVE-2020-11076

Weakness enumeration for CVE-2020-11076

GitHub Security Advisory for CVE-2020-11076

OS Trackers for CVE-2020-11076

Affected software / configurations for CVE-2020-11076

References for CVE-2020-11076