CVE-2024-45614
Puma is a Ruby/Rack web server built for parallelism. In affected versions clients could clobber values set by intermediate proxies (such as X-Forwarded-For) by providing a underscore version of the same header (X-Forwarded_For). Any users relying on proxy set variables is affected. v6.4.3/v5.6.9 now discards any headers using underscores if the non-underscore version also exists. Effectively, allowing the proxy defined headers to always win. Users are advised to upgrade. Nginx has a underscores_in_headers configuration variable to discard these headers at the proxy level as a mitigation. Any users that are implicitly trusting the proxy defined headers for security should immediately cease doing so until upgraded to the fixed versions.
CVSS
- Base score
- 5.4
- Version
- 3.1
- Vector
- CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
Exploitation probability (EPSS)
- Probability of exploitation in the next 30 days
- 0.64 %
- Percentile among all scored CVEs
- 51
- Score date
- 11/2/2026
EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).
Public exploits
Exploit code or detection templates are publicly available. This is not the same as confirmed active exploitation (KEV), but it raises the risk: patch with priority.
- Proof of concept on GitHub (unverified) · List of proofs of concept on GitHub
⚠️ GitHub proofs of concept are not verified: some are fake or contain malware. Never run them outside an isolated lab.
Affected technologies (1)
CWEs
- CWE-639
- CWE-444
References
Raw JSON (NVD)
Show
{
"id": "CVE-2024-45614",
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"lang": "en",
"value": "Puma is a Ruby/Rack web server built for parallelism. In affected versions clients could clobber values set by intermediate proxies (such as X-Forwarded-For) by providing a underscore version of the same header (X-Forwarded_For). Any users relying on proxy set variables is affected. v6.4.3/v5.6.9 now discards any headers using underscores if the non-underscore version also exists. Effectively, allowing the proxy defined headers to always win. Users are advised to upgrade. Nginx has a underscores_in_headers configuration variable to discard these headers at the proxy level as a mitigation. Any users that are implicitly trusting the proxy defined headers for security should immediately cease doing so until upgraded to the fixed versions."
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"value": "Puma es un servidor web Ruby/Rack creado para el paralelismo. En las versiones afectadas, los clientes podían alterar los valores establecidos por los servidores proxy intermedios (como X-Forwarded-For) al proporcionar una versión con guiones bajos del mismo encabezado (X-Forwarded_For). Todos los usuarios que dependan de las variables establecidas por el proxy se ven afectados. v6.4.3/v5.6.9 ahora descarta cualquier encabezado que utilice guiones bajos si también existe la versión sin guiones bajos. De hecho, permite que los encabezados definidos por el proxy siempre prevalezcan. Se recomienda a los usuarios que actualicen. Nginx tiene una variable de configuración underscores_in_headers para descartar estos encabezados a nivel de proxy como mitigación. Todos los usuarios que confíen implícitamente en los encabezados definidos por el proxy por razones de seguridad deben dejar de hacerlo de inmediato hasta que se actualicen a las versiones corregidas."
}
],
"lastModified": "2026-06-17T07:54:34.120",
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