CVE-2025-23419: nginx Auth Bypass — Fix

Description

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.

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CVSS v3.1 Score

4.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Weakness Type (CWE)

CWE-863 Incorrect Authorization

Affected Products

Vendor	Product	Versions
f5	nginx	1.11.4 — 1.26.3
f5	nginx	1.27.0 — 1.27.4
f5	nginx_plus	r28 — r32
f5	nginx_plus	All
f5	nginx_plus	All
f5	nginx_plus	All
f5	nginx_plus	All
debian	debian_linux	All

References

Advisories & Patches

https://my.f5.com/manage/s/article/K000149173

Other References

http://www.openwall.com/lists/oss-security/2025/02/05/8 https://lists.debian.org/debian-lts-announce/2025/03/msg00017.html

Frequently Asked Questions

What is CVE-2025-23419? +

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. It has a CVSS v3.1 base score of 4.3 (MEDIUM).

How severe is CVE-2025-23419? +

CVE-2025-23419 has a CVSS v3.1 score of 4.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-23419? +

CVE-2025-23419 affects products from debian, f5, specifically: debian_linux, nginx, nginx_plus. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-23419? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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