CVE-2026-47736
Description
A flaw was found in Puma, a Ruby/Rack web server. When PROXY protocol v1 support is enabled, a remote attacker can continuously send data without proper termination. This causes the server to consume an increasing amount of memory and CPU resources, leading to a Denial of Service (DoS) where the server becomes unresponsive or crashes.
Statement
This issue only affects Puma deployments that explicitly enable the non-default proxy_protocol: :v1 remote-address configuration (set_remote_address proxy_protocol: :v1). An unauthenticated network attacker able to open a TCP connection to such a listener can send bytes without a terminating CRLF, causing unbounded growth of an internal pre-parse buffer and a potential denial of service. Deployments that do not enable this configuration are not affected by this specific issue.
Mitigation
Upgrade to Puma 7.2.1 (7.x branch) or 8.0.2 (8.x branch), whichever applies to the deployed release line. If an immediate upgrade is not possible, remove or comment out the set_remote_address proxy_protocol: :v1 configuration directive if it is not required, or restrict direct network access to the affected Puma listener to trusted load balancers or reverse proxies only.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
When allocating resources without limits, an attacker could prevent other systems, applications, or processes from accessing the same type of resource. It can be easy for an attacker to consume many resources by rapidly making many requests or causing larger resources to be used than is needed.
Frequently Asked Questions
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