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Response snapshot Nov 2, 2026, 23:21 UTC

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VulnerabilityCVE-2026-47737

Puma PROXY Protocol v1 Accepts Repeated Protocol Headers on Persistent Connections

Puma is vulnerable to source IP spoofing when set_remote_address proxy_protocol: :v1 is enabled and persistent connections are used. PROXY protocol v1 is a connection-level protocol. [Support was added to Puma in v5.5.0](https://github.com/puma/puma/issues/2651).

At a glance

Exploited
Not known
Severity
7.5 High (CVSS 3.1)
Chance of exploitation
0.2% in the next 30 days
Sources
1 source

What to do

GitHub lists first patched versions: puma: 8.0.2; puma: 7.2.1. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-2vqw-3mp8-cgmx (opens a new tab)

What happened

Impact

Puma is vulnerable to source IP spoofing when set_remote_address proxy_protocol: :v1 is enabled and persistent connections are used.

PROXY protocol v1 is a connection-level protocol. [Support was added to Puma in v5.5.0](https://github.com/puma/puma/issues/2651). A proxy sends one PROXY header at the beginning of a TCP connection, before any HTTP data. Puma incorrectly re-parsed PROXY protocol headers after each keep-alive request on the same connection.

An attacker able to send HTTP requests through a trusted proxy could therefore inject a second PROXY header between HTTP requests. Puma would treat the injected header as authoritative for the next request and overwrite REMOTE_ADDR.

Continue reading

This can mislead applications or middleware that use REMOTE_ADDR for security decisions, rate limiting, auditing, or allow/deny lists.

Only deployments that explicitly enable PROXY protocol v1 are affected, and will have set:

set_remote_address proxy_protocol: :v1

Puma's default configuration is not affected. Deployments that do not use persistent connections to Puma are also not expected to be affected by this issue.

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

Users can also disable persistent connections to Puma, for example:

enable_keep_alives false

References

- [HAProxy PROXY protocol specification](https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt) - [CVE-2025-31135 / GHSA-c2c3-pqw5-5p7c: go-guerrilla repeated PROXY command source IP spoofing](https://github.com/phires/go-guerrilla/security/advisories/GHSA-c2c3-pqw5-5p7c) - [Puma set_remote_address documentation](https://github.com/puma/puma/blob/master/lib/puma/dsl.rb)

Affected package ranges reported by GitHub: puma: >= 8.0.0, < 8.0.2 puma: >= 5.5.0, < 7.2.1

Scores and how they were measured

CVSS base severity

7.5

Version 3.1As of

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.2%

Scored Percentile 7.3%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-2vqw-3mp8-cgmx (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-2vqw-3mp8-cgmx, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-47737, scored 2026-11-02. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, November 2). Puma PROXY Protocol v1 Accepts Repeated Protocol Headers on Persistent Connections (CVE-2026-47737). https://kevwire.com/record/CVE-2026-47737

MLA

"Puma PROXY Protocol v1 Accepts Repeated Protocol Headers on Persistent Connections (CVE-2026-47737)." KEVWire, 2 Nov. 2026, kevwire.com/record/CVE-2026-47737.

Chicago

KEVWire. "Puma PROXY Protocol v1 Accepts Repeated Protocol Headers on Persistent Connections (CVE-2026-47737)." Last modified November 2, 2026. https://kevwire.com/record/CVE-2026-47737.

Evidence summary (plain text)

Puma PROXY Protocol v1 Accepts Repeated Protocol Headers on Persistent Connections (Jun 9, 2026).
Puma is vulnerable to source IP spoofing when set_remote_address proxy_protocol: :v1 is enabled and persistent connections are used.

PROXY protocol v1 is a connection-level protocol. [Support was added to Puma in v5.5.0](https://github.com/puma/puma/issues/2651). A proxy sends one PROXY header at the beginning of a TCP connection, before any HTTP data. Puma incorrectly re-parsed PROXY protocol headers after each keep-alive request on the same connection. An attacker able to send HTTP requests through a trusted proxy could therefore inject a second PROXY header between HTTP requests.
CVSS 7.5 (version 3.1; evidence as of Nov 2, 2026; https://github.com/advisories/GHSA-2vqw-3mp8-cgmx).
EPSS 0.2% for the following 30 days, scored Nov 2, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-47737&date=2026-11-02).
Sources:
GitHub-reviewed advisory GHSA-2vqw-3mp8-cgmx: https://github.com/advisories/GHSA-2vqw-3mp8-cgmx
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-47737&date=2026-11-02
Record ID: CVE-2026-47737.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Nov 2, 2026, 23:21 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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