High [CVE-2026-47736] Denial of Service due to unbounded memory growth in PROXY protocol v1
This high-severity Red Hat Linux advisory covers CVE-2026-47736.
Android app · Google Play
Monitor future Red Hat Linux CVEs from your phone.
Choose a whole vendor or a precise platform, then receive matching security advisories by phone notification, email, or both. Coverage follows 32 official vendor sources and 160+ reviewed platform categories.
Summary
Puma is a Ruby/Rack web server built for parallelism.
From 5.5.0 until 7.2.1 and 8.0.2, when PROXY protocol v1 support is enabled, Puma reads incoming bytes into an internal buffer while waiting for CRLF to determine whether a PROXY v1 line is present, allowing an attacker that continuously sends bytes without CRLF to cause unbounded in-process memory growth and additional CPU cost from repeatedly scanning the growing buffer.
This issue is fixed in versions 7.2.1 and 8.0.2. 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. 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.
Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-770.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 6 days ago·verify at source
- 7.2.1
- 8.0.2
Official advisory · high-confidence parse· fetched 6 days ago·verify at source
Mitigation checklist
- 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.
Official advisory · high-confidence parse· fetched 6 days ago·verify at source
Discussion(0)
No comments yet. Share field notes, upgrade gotchas, or questions — verify against the vendor advisory before acting on community advice.
Sign in to join the discussion.