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CVE-2026-47737

Puma PROXY Protocol v1 Accepts Repeated Protocol Headers on Persistent Connections

7.5 HighFix available

Puma is a Ruby/Rack web server built for parallelism. From 5.5.0 until 7.2.1 and 8.0.2, Puma is vulnerable to source IP spoofing when set_remote_address proxy_protocol: :v1 is enabled and persistent connections are used because Puma incorrectly re-parses PROXY protocol headers after each keep-alive request on the same connection, allowing an attacker to inject a second PROXY header and overwrite REMOTE_ADDR. This issue is fixed in versions 7.2.1 and 8.0.2.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
High
Availability
None

Exploit likelihood

0.18%Up 0.2 points since Jun 12, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.5

Puma PROXY Protocol v1 Accepts Repeated Protocol Headers on Persistent Connections

Puma is a Ruby/Rack web server built for parallelism. From 5.5.0 until 7.2.1 and 8.0.2, Puma is vulnerable to source IP spoofing when set_remote_address proxy_protocol: :v1 is enabled and persistent connections are used because Puma incorrectly re-parses PROXY protocol headers after each keep-alive request on the same connection, allowing an attacker to inject a second PROXY header and overwrite REMOTE_ADDR. This issue is fixed in versions 7.2.1 and 8.0.2.

Record
CVE-2026-47737
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness
CWE-290, CWE-345
Updated
2026-11-02
EUVDEUVD-2026-44427 7.5

Puma is a Ruby/Rack web server built for parallelism. From 5.5.0 until 7.2.1 and 8.0.2, Puma is vulnerable to source IP spoofing when set_remote_address proxy_protocol: :v1 is enabled and persistent connections are used because Puma incorrectly re-parses PROXY protocol headers after each keep-alive request on the same connection, allowing an attacker to inject a second PROXY header and overwrite REMOTE_ADDR. This issue is fixed in versions 7.2.1 and 8.0.2.

Record
EUVD-2026-44427
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-2vqw-3mp8-cgmx 7.5

Puma PROXY Protocol v1 Accepts Repeated Protocol Headers on Persistent Connections

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. 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.

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

Record
GHSA-2vqw-3mp8-cgmx
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness
CWE-290, CWE-345
Updated
2026-11-03
NVD 7.5

Puma is a Ruby/Rack web server built for parallelism. From 5.5.0 until 7.2.1 and 8.0.2, Puma is vulnerable to source IP spoofing when set_remote_address proxy_protocol: :v1 is enabled and persistent connections are used because Puma incorrectly re-parses PROXY protocol headers after each keep-alive request on the same connection, allowing an attacker to inject a second PROXY header and overwrite REMOTE_ADDR. This issue is fixed in versions 7.2.1 and 8.0.2.

Record
CVE-2026-47737
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness
CWE-290, CWE-345
Updated
2026-11-02
OSV 7.5

Puma PROXY Protocol v1 Accepts Repeated Protocol Headers on Persistent Connections

Puma is a Ruby/Rack web server built for parallelism. From 5.5.0 until 7.2.1 and 8.0.2, Puma is vulnerable to source IP spoofing when set_remote_address proxy_protocol: :v1 is enabled and persistent connections are used because Puma incorrectly re-parses PROXY protocol headers after each keep-alive request on the same connection, allowing an attacker to inject a second PROXY header and overwrite REMOTE_ADDR. This issue is fixed in versions 7.2.1 and 8.0.2.

Record
CVE-2026-47737
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness
CWE-290, CWE-345
Updated
2026-11-02
OSVDEBIAN-CVE-2026-47737 7.5

Puma is a Ruby/Rack web server built for parallelism. From 5.5.0 until 7.2.1 and 8.0.2, Puma is vulnerable to source IP spoofing when set_remote_address proxy_protocol: :v1 is enabled and persistent connections are used because Puma incorrectly re-parses PROXY protocol headers after each keep-alive request on the same connection, allowing an attacker to inject a second PROXY header and overwrite REMOTE_ADDR. This issue is fixed in versions 7.2.1 and 8.0.2.

Record
DEBIAN-CVE-2026-47737
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Updated
2026-11-02
OSVGHSA-2vqw-3mp8-cgmx 7.5

Puma PROXY Protocol v1 Accepts Repeated Protocol Headers on Persistent Connections

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. 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.

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

Record
GHSA-2vqw-3mp8-cgmx
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness
CWE-290, CWE-345
Updated
2026-11-03
OSVUBUNTU-CVE-2026-47737 7.5

Puma is a Ruby/Rack web server built for parallelism. From 5.5.0 until 7.2.1 and 8.0.2, Puma is vulnerable to source IP spoofing when set_remote_address proxy_protocol: :v1 is enabled and persistent connections are used because Puma incorrectly re-parses PROXY protocol headers after each keep-alive request on the same connection, allowing an attacker to inject a second PROXY header and overwrite REMOTE_ADDR. This issue is fixed in versions 7.2.1 and 8.0.2.

Record
UBUNTU-CVE-2026-47737
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
puma
RubyGems
 8.0.0 up to 8.0.2
8.0.2
puma
RubyGems
 5.5.0 up to 7.2.1
7.2.1
puma
Debian:12
 before 5.6.5-3+deb12u2, plus listed versions
5.6.5-35.6.5-3+deb12u1
5.6.5-3+deb12u2
puma
Debian:13
 All versions, plus listed versions
6.6.0-48.0.2-18.0.2-28.0.2-3
 None known
puma
Debian:14
 before 8.0.2-1, plus listed versions
6.6.0-4
8.0.2-1
puma
RubyGems
 8.0.0 up to 8.0.2, plus listed versions
8.0.1
8.0.2
puma
RubyGems
 5.5.0 up to 7.2.1, plus listed versions
5.5.15.5.25.6.05.6.15.6.2
Show 31 moreShow less
5.6.45.6.55.6.65.6.75.6.85.6.96.0.06.0.16.0.26.1.06.1.16.2.06.2.16.2.26.3.06.3.16.4.06.4.16.4.26.4.36.5.06.6.06.6.17.0.07.0.0.pre17.0.17.0.27.0.37.0.47.1.07.2.0
7.2.1
puma
Ubuntu:Pro:20.04:LTS
 All versions, plus listed versions
3.12.0-2ubuntu13.12.0-4ubuntu13.12.4-1ubuntu23.12.4-1ubuntu2+esm13.12.4-1ubuntu2+esm2
 None known
puma
Ubuntu:Pro:22.04:LTS
 All versions, plus listed versions
4.3.6-1ubuntu45.5.2-2ubuntu25.5.2-2ubuntu2+esm15.5.2-2ubuntu2+esm2
 None known
puma
Ubuntu:24.04:LTS
 All versions, plus listed versions
5.6.5-4ubuntu25.6.5-4ubuntu36.4.2-4ubuntu16.4.2-4ubuntu36.4.2-4ubuntu46.4.2-4ubuntu4.3
 None known
puma
Ubuntu:26.10
 All versions, plus listed versions
6.6.0-4build18.0.2-3build1
 None known
puma
Ubuntu:26.04:LTS
 All versions, plus listed versions
6.6.0-46.6.0-4build1
 None known

History

History
RecordedChangedSources
referencesGitHub Advisories, OSV
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-47737 is a high vulnerability (CVSS 7.5) in Puma, published June 9, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.18%, the 7th percentile. Fixed in puma 8.0.2.

References

Show 11 moreShow less
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