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Vulnerabilities

Security fix · CVE-2026-47736

Puma PROXY Protocol v1 Parser Allows Remote Memory Exhaustion

Published Jun 8, 2026 · catalog updated Nov 2, 2026 · Puma PROXY Protocol v1

Last checked Nov 7, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-47736. EPSS is 0.35%. Act only if a listed version of Puma PROXY Protocol v1 is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Puma PROXY Protocol v1).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.35%
Remediation
Advisory link
Affected products
RubyGems puma

### Impact [PROXY protocol support for Puma](https://github.com/puma/puma/issues/2651) 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:** ### Patches Users should upgrade to versions 7.2.1 or 8.0.2. ### Workarounds - Disable PROXY protocol v1 parsing if it is not required: - 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 - [HAProxy PROXY protocol specification](https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt) - [CWE-400: Uncontrolled Resource Consumption](https://cwe.mitre.org/data/definitions/400.html) - [CWE-770: Allocation of Resources Without Limits or Throttling](https://cwe.mitre.org/data/definitions/770.html) - [Puma documentation](https://github.com/puma/puma/blob/master/lib/puma/dsl.rb) - [Puma client PROXY protocol parsing code](https://github.com/puma/puma/blob/master/lib/puma/client.rb) - [Puma constants, including ](https://github.com/puma/puma/blob/master/lib/puma/const.rb)

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • RubyGems puma5.5.0 → 7.2.1
  • RubyGems puma8.0.0 → 8.0.2

How to fix CVE-2026-47736

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-47736. EPSS is 0.35%. Act only if a listed version of Puma PROXY Protocol v1 is installed.

Which versions are affected?

Compare what you have installed with 5.5.0 → 7.2.1, 8.0.0 → 8.0.2. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-400: Uncontrolled Resource Consumption. EPSS 0.35%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Jun 8, 2026 · GitHub Advisory Database

    Detected

    ### Impact [PROXY protocol support for Puma](https://github.com/puma/puma/issues/2651) 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 bu

  2. Nov 2, 2026 · GitHub Advisory Database

    Fix available

    puma fixed in 8.0.2; puma fixed in 7.2.1

  3. Nov 2, 2026 · GitHub Advisory Database

    Fix available

    puma fixed in 8.0.2

  4. Nov 2, 2026 · GitHub Advisory Database

    Fix available

    puma fixed in 7.2.1

  5. Nov 2, 2026 · GitHub Advisory Database

    Updated

    ### Impact [PROXY protocol support for Puma](https://github.com/puma/puma/issues/2651) 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 bu

Sources

References

Freshness

Last verified in this catalog Nov 4, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • GitHub Advisory DatabaseNov 7, 2026
  • OpenSSF OSV / OSV ScannerNov 7, 2026
  • CVE.orgNov 4, 2026