CVE-2026-47737
Description
A flaw was found in Puma, a Ruby/Rack web server. When set_remote_address proxy_protocol: :v1 is enabled and persistent connections are used, Puma incorrectly re-parses PROXY protocol headers after each keep-alive request on the same connection. This allows a remote attacker to inject a second PROXY header, leading to source IP (Internet Protocol) spoofing and potentially impacting security logging or access control decisions.
Statement
This flaw only affects Puma deployments that explicitly enable set_remote_address proxy_protocol: :v1 together with persistent (keep-alive) connections to the proxy. This is not Puma default configuration.
Mitigation
Upgrade puma to 7.2.1 or 8.0.2 (or later). If an immediate upgrade is not possible, remove the `set_remote_address proxy_protocol: :v1` configuration, or disable persistent connections (`enable_keep_alives false`), to prevent PROXY protocol v1 header re-parsing on the same connection.
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 | High | N/A | High |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Understanding the Weakness (CWE)
Access Control
Technical Impact: Bypass Protection Mechanism
Frequently Asked Questions
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