CVE-2026-47737 is a high-severity security vulnerability in puma (rubygems), affecting versions >= 8.0.0, < 8.0.2. It is fixed in 8.0.2, 7.2.1.
Impact Puma is vulnerable to source IP spoofing when setremoteaddress proxyprotocol: :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 REMOTEADDR. This can mislead applications or middleware that use REMOTEADDR for security decisions, rate limiting, auditing, or allow/deny lists. Only deployments that explicitly enable PROXY protocol v1 are affected, and will have set: 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: ruby # remove/comment this: # setremoteaddress proxyprotocol: :v1 Users can also disable persistent connections to Puma, for example: References HAProxy PROXY protocol specification CVE-2025-31135 / GHSA-c2c3-pqw5-5p7c: go-guerrilla repeated PROXY command source IP spoofing Puma setremoteaddress documentation
CVE-2026-47737 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (8.0.2, 7.2.1). Upgrading removes the vulnerable code path.
rubygems
puma (>= 8.0.0, < 8.0.2)puma (>= 5.5.0, < 7.2.1)puma → 8.0.2 (rubygems)puma → 7.2.1 (rubygems)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter instead of chasing every advisory.
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Upgrade the following packages to resolve this vulnerability:
puma to 8.0.2 or laterpuma to 7.2.1 or laterKodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2026-47737 is a high-severity security vulnerability in puma (rubygems), affecting versions >= 8.0.0, < 8.0.2. It is fixed in 8.0.2, 7.2.1.
CVE-2026-47737 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
puma (rubygems) versions >= 8.0.0, < 8.0.2 is affected.
Yes. CVE-2026-47737 is fixed in 8.0.2, 7.2.1. Upgrade to this version or later.
Whether CVE-2026-47737 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
puma to 8.0.2 or laterpuma to 7.2.1 or later