CVE-2020-11077

HTTP Smuggling via Transfer-Encoding Header in Puma

HIGH
7.5
CVSS Score
Published: May 22, 2020 at 02:55 PM UTC
Updated: June 17, 2026 at 02:49 AM UTC
4 products affected across 4 vendorsDebian LinuxFedoraLeap

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Severity
HIGH7.5
Exploit prediction
EPSS 3%

Description

In Puma (RubyGem) before 4.3.5 and 3.12.6, a client could smuggle a request through a proxy, causing the proxy to send a response back to another unknown client. If the proxy uses persistent connections and the client adds another request in via HTTP pipelining, the proxy may mistake it as the first request's body. Puma, however, would see it as two requests, and when processing the second request, send back a response that the proxy does not expect. If the proxy has reused the persistent connection to Puma to send another request for a different client, the second response from the first client will be sent to the second client. This is a similar but different vulnerability from CVE-2020-11076. The problem has been fixed in Puma 3.12.6 and Puma 4.3.5.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Puma· Pumarubygems
95%
v < 3.12.6v < 4.3.53.0.0 ≤ v < 3.12.64.0.0 ≤ v < 4.3.5
Affected range stops below 3.12.6, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.3.5, so it looks safe — our inference, not a vendor statement

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
HIGH
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-444

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