Live › vulnerability › CVE-2026-47736
Puma buffers incoming bytes without limit while waiting for a PROXY protocol v1 line terminated by CRLF. A single unauthenticated TCP connection that never sends CRLF can grow memory without bound and drive CPU cost, causing process or container out-of-memory crashes.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-11-02 22:13 UTC, 0h before NVD. All times on this page are UTC.
Only Puma servers with PROXY protocol v1 parsing enabled through set_remote_address proxy_protocol: :v1 are exposed; default configurations are not. Teams that run Puma behind a load balancer and accept direct client connections on the Puma port are the most exposed, and deployments where only trusted proxies can reach Puma can skip the urgent change.
| Product | Ecosystem | Affected | Fixed in |
|---|---|---|---|
| puma | rubygems | >= 8.0.0, < 8.0.2 | 8.0.2 |
| puma | rubygems | >= 5.5.0, < 7.2.1 | 7.2.1 |
bundle exec puma --version, and compare against the affected ranges.set_remote_address proxy_protocol: :v1; only this non-default setting is affected.>= 8.0.0, < 8.0.2: upgrade to 8.0.2>= 5.5.0, < 7.2.1: upgrade to 7.2.1Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
PROXY protocol support for Puma was added in version 5.5.0.
When PROXY protocol v1 support is enabled, Puma reads incoming bytes into an internal buffer. It waits for "\r\n" to determine whether a PROXY v1 line is present. If an attacker opens a TCP connection and continuously sends bytes without CRLF, Puma keeps appending to this pre-parse buffer.
This can cause unbounded in-process memory growth and additional CPU cost from repeatedly scanning the growing buffer for CRLF. A single, unauthenticated TCP connection can drive significant memory growth and may cause process/container OOM or degraded availability.
Only Puma servers using the following non-default config are affected:
set_remote_address proxy_protocol: :v1
Users should upgrade to versions 7.2.1 or 8.0.2.
# remove/comment this:
# set_remote_address proxy_protocol: :v1
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