CVE-2025-23419
MEDIUMCVSS Vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
3Description
When multiple server blocks are configured to share the same IP address and port, an attacker can use session resumption to bypass client certificate authentication requirements on these servers. This vulnerability arises when TLS Session Tickets https://nginx.org/en/docs/http/ngx_http_ssl_module.html#ssl_session_ticket_key are used and/or the SSL session cache https://nginx.org/en/docs/http/ngx_http_ssl_module.html#ssl_session_cache are used in the default server and the default server is performing client certificate authentication. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
Analysis
When multiple server blocks are configured to share the same IP address and port, an attacker can use session resumption to bypass client certificate authentication requirements on these servers. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
Technical Context
This vulnerability is classified as Incorrect Authorization (CWE-863), which allows attackers to bypass authorization checks to access restricted resources. When multiple server blocks are configured to share the same IP address and port, an attacker can use session resumption to bypass client certificate authentication requirements on these servers. This vulnerability arises when TLS Session Tickets https://nginx.org/en/docs/http/ngx_http_ssl_module.html#ssl_session_ticket_key are used and/or the SSL session cache https://nginx.org/en/docs/http/ngx_http_ssl_module.html#ssl_session_cache are used in the default server and the default server is performing client certificate authentication. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated. Affected products include: F5 Nginx, F5 Nginx Plus, Debian Debian Linux.
Affected Products
F5 Nginx, F5 Nginx Plus, Debian Debian Linux.
Remediation
No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Review and test authorization logic, implement consistent access control checks, use centralized authorization framework.
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External POC / Exploit Code
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