CVE-2026-47736

HIGHPre-NVD 7.57.5
EchelonGraph scoreLOW confidence

This high-severity CVE scores 7.5 under the CNA's CVSS (NVD's own analysis pending). EPSS exploit probability: 0.1%, top 78% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: cna:github_m, epss
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.5Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Puma PROXY Protocol v1 Parser Allows Remote Memory Exhaustion

Impact

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

Patches

Users should upgrade to versions 7.2.1 or 8.0.2.

Workarounds

  • Disable PROXY protocol v1 parsing if it is not required:

# remove/comment this:
   # set_remote_address proxy_protocol: :v1
  • Restrict direct network access to Puma listeners using PROXY protocol:
  • Only allow trusted load balancers/reverse proxies to connect.
  • Block arbitrary client TCP access with firewall/security group rules.

Resources

CVSS v3
7.5
EG Score
7.5(low)
EPSS
21.9%
KEV
Not listed

Published

June 8, 2026

Last Modified

June 8, 2026

Vendor Advisories for CVE-2026-47736(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
RubyGems(1)
PackageVulnerable rangeFixed inDependents
puma5.5.0 ... 7.2.0 (37 versions)7.2.1—

Frequently asked(5)

What is CVE-2026-47736?
CVE-2026-47736 is a high vulnerability published on June 8, 2026. Puma PROXY Protocol v1 Parser Allows Remote Memory Exhaustion Impact 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…
When was CVE-2026-47736 disclosed?
CVE-2026-47736 was first published in the National Vulnerability Database on June 8, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-47736 actively exploited?
CVE-2026-47736 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 21.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-47736?
CVE-2026-47736 has a CVSS v4.0 base score of 7.5 (CNA self-assessment; NVD's own analysis pending). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-47736?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-47736, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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