Skip to content
VulniPulse
Sign in
Advisory severityHigh7.5Red Hat Linux

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.

Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.

CVE-2026-47736 Source published Source updated

VulniPulse record published Record updated

CVE-2026-47736
Affected products & platforms
Red Hat LinuxUnclassified
Open source advisory

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.

Is CVE-2026-47736 exploited?

No exploitation is reported in the sources VulniPulse tracks: CVE-2026-47736 is not in the CISA KEV catalog (checked ) and this advisory does not report exploitation. That is not proof the vulnerability cannot be exploited.

How do I fix CVE-2026-47736?

Upgrade to a fixed release named by Red Hat:

  • 7.2.1
  • 8.0.2

Confirm against the vendor advisory before you patch.

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

Fixed versions
  • 7.2.1
  • 8.0.2

Official advisory · high-confidence parse· fetched 6 days ago·verify at source

Mitigation checklist

Recommended fix / mitigation
  • 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

Get an email when Red Hat Linux publishes the next one.

See Red Hat Linux's last 90 days of advisories first. Then choose one product with live alerts free for life, or a free month of real-time alerts on everything with the severity, the fixed version and the vendor's link (card needed, then US$15/month; we email you before the first charge).

Alert me about Red Hat Linux

More Red Hat Linux advisories

All Red Hat Linux advisories

iPhone and Android apps · New on the App Store

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 34 official vendor sources and 160+ reviewed platform categories.

Download on the App StoreGet CVE alerts on AndroidSee app features

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.