{"id":"CVE-2026-47736","aliases":["GHSA-qpgp-93vx-g8v8"],"title":"Puma PROXY Protocol v1 Parser Allows Remote Memory Exhaustion ","summary":"Puma PROXY Protocol v1 Parser Allows Remote Memory Exhaustion ","severity":"high","cvss":7.5,"cwe":["CWE-400"],"vendor":"puma","product":"puma","ecosystem":"rubygems","affected":["puma >= 8.0.0, < 8.0.2","puma >= 5.5.0, < 7.2.1"],"patched":["puma 8.0.2","puma 7.2.1"],"published":"2026-06-08","updated":"2026-06-08","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-qpgp-93vx-g8v8","references":[{"url":"https://github.com/puma/puma/security/advisories/GHSA-qpgp-93vx-g8v8"},{"url":"https://github.com/rubysec/ruby-advisory-db/blob/master/gems/puma/CVE-2026-47736.yml"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-47736"},{"url":"https://github.com/advisories/GHSA-qpgp-93vx-g8v8"}],"tags":["ghsa","rubygems"],"ingestedAt":"2026-07-07T15:41:59.610Z","epss":0.0063,"epssPercentile":0.4848,"slug":"CVE-2026-47736","body":"## Overview\n\n### Impact\n\n[PROXY protocol support for Puma](https://github.com/puma/puma/issues/2651) was added in version 5.5.0.\n\nWhen 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.\n\nThis 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.\n\n**Only Puma servers using the following non-default config are affected:**\n\n```ruby\n   set_remote_address proxy_protocol: :v1\n```\n\n### Patches\n\nUsers should upgrade to versions 7.2.1 or 8.0.2.\n\n### Workarounds\n\n- Disable PROXY protocol v1 parsing if it is not required:\n\n ```ruby\n   # remove/comment this:\n   # set_remote_address proxy_protocol: :v1\n ```\n\n - Restrict direct network access to Puma listeners using PROXY protocol:\n     - Only allow trusted load balancers/reverse proxies to connect.\n     - Block arbitrary client TCP access with firewall/security group rules.\n\n### Resources\n- [HAProxy PROXY protocol specification](https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt)\n- [CWE-400: Uncontrolled Resource Consumption](https://cwe.mitre.org/data/definitions/400.html)\n- [CWE-770: Allocation of Resources Without Limits or Throttling](https://cwe.mitre.org/data/definitions/770.html)\n- [Puma `set_remote_address` documentation](https://github.com/puma/puma/blob/master/lib/puma/dsl.rb)\n- [Puma client PROXY protocol parsing code](https://github.com/puma/puma/blob/master/lib/puma/client.rb)\n- [Puma constants, including `PROXY_PROTOCOL_V1_REGEX`](https://github.com/puma/puma/blob/master/lib/puma/const.rb)\n\n## Affected packages\n\n- `puma >= 8.0.0, < 8.0.2`\n- `puma >= 5.5.0, < 7.2.1`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `puma 8.0.2`\n- `puma 7.2.1`","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}