CVE-2025-23419: Debian Linux

Medium severity, CVSS 4.3. EPSS: 2.8% chance of exploitation in the next 30 days.

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

• Debian Debian Linux: version 11.0 only
• F5 Nginx: from 1.11.4, before 1.26.3 (fixed in 1.26.3); from 1.27.0, before 1.27.4 (fixed in 1.27.4)
• F5 Nginx Plus: from r28, before r32 (fixed in r32); version r32 only; version r33 only

Published 2025-02-05. Last modified 2026-06-17.