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… (CVE-2026-47737)
Description
Puma web server versions from 5.5.0 up to 7.2.1 and 8.0.2 are vulnerable to source IP spoofing when the set_remote_address proxy_protocol: :v1 option is enabled and persistent connections are used. The vulnerability arises 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 the REMOTE_ADDR value. This issue is fixed in versions 7.2.1 and 8.0.2.
CVSS v3.1
Score 7.5high
Affected software
pkg:deb/ubuntu/puma?arch=source&distro=esm-apps/focalpkg:deb/ubuntu/puma?arch=source&distro=esm-apps/jammypkg:deb/ubuntu/puma?arch=source&distro=noblepkg:deb/ubuntu/puma?arch=source&distro=stonkingpkg:deb/ubuntu/puma?arch=source&distro=resoluteRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Puma, a Ruby/Rack web server designed for parallelism, suffers from a source IP spoofing vulnerability in versions from 5.5.0 until 7.2.1 and 8.0.2 when the set_remote_address proxy_protocol: :v1 feature is enabled. The vulnerability occurs because Puma re-parses PROXY protocol headers on persistent connections after each keep-alive request, which allows an attacker to inject an additional PROXY header. This injection overwrites the REMOTE_ADDR environment variable, enabling spoofing of the source IP address. The flaw is addressed in Puma versions 7.2.1 and 8.0.2.
Potential Impact
An attacker can spoof the source IP address seen by the Puma server by injecting a second PROXY protocol header on persistent connections. This can lead to incorrect IP-based access control, logging, or other security mechanisms relying on REMOTE_ADDR, potentially allowing unauthorized access or evasion of IP-based restrictions. There is no direct confidentiality or availability impact reported.
Mitigation Recommendations
Upgrade Puma to version 7.2.1 or 8.0.2 or later, where this vulnerability is fixed. If upgrading is not immediately possible, consider disabling the set_remote_address proxy_protocol: :v1 feature or avoid using persistent connections with this setting until patched. Patch status is confirmed fixed in versions 7.2.1 and 8.0.2.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-47737
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:Pro:20.04:LTS","Ubuntu:Pro:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:26.10","Ubuntu:26.04:LTS"]
- Cvss Version
- 3.1
Threat ID: 6ad3f6312cdf04f656664f0e
Added to database: 10/17/2026, 22:26:57 UTC
Last enriched: 10/18/2026, 01:08:43 UTC
Last updated: 10/18/2026, 01:08:43 UTC
Views: 2
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