CVE-2026-47737
HighCVSS 7.5Exploitation Probability (EPSS)
Low risk7th percentile - higher than 7% of all known CVEs
Summary
Puma versions 5.5.0 through 7.2.1 and 8.0.2 are vulnerable to source IP spoofing. When proxy_protocol: :v1 is enabled and persistent connections are used, Puma incorrectly re-parses PROXY headers after each keep-alive request, allowing an attacker to inject a second PROXY header and overwrite REMOTE_ADDR.
Risk Assessment
An attacker can spoof a trusted IP address, potentially bypassing IP-based authentication, auditing, or access controls.
Recommendation
Upgrade Puma to version 7.2.1 or 8.0.2 immediately, depending on your branch.
Other vulnerabilities in Puma
See all- CVE-2026-47736High
A vulnerability in Puma (versions 5.5.0 through 7.2.1 and 8.0.2) with PROXY protocol v1 support enabled allows an attacker to continuously send bytes without CRLF, causing unbounded in-process memory growth and additional CPU cost from repeatedly scanning the growing buffer.
- CVE-2023-40175High
Puma, a Ruby/Rack web server, prior to versions 6.3.1 and 5.6.7, exhibited incorrect behavior when parsing chunked transfer encoding bodies and zero-length Content-Length headers, allowing for HTTP request smuggling.
Original NVD description (English source)
Puma is a Ruby/Rack web server built for parallelism. From 5.5.0 until 7.2.1 and 8.0.2, Puma is vulnerable to source IP spoofing when set_remote_address proxy_protocol: :v1 is enabled and persistent connections are used because Puma incorrectly re-parses PROXY protocol headers after each keep-alive request on the same connection, allowing an attacker to inject a second PROXY header and overwrite REMOTE_ADDR. This issue is fixed in versions 7.2.1 and 8.0.2.