What is CVE-2026-40435?

CVE-2026-40435 is a medium-severity vulnerability in F5 Big-ip, classified under Unprotected Alternate Channel. CVSS score: 5.3/10. Published 2026-05-13.

How severe is CVE-2026-40435?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in F5 Big-ip

CVE-2026-40435

When configured, IP-based access restrictions for httpd do not cover all endpoints, which may allow connections from blocked addresses. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

EPSS: 0.001 (19.7th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.

Affected products

F5 Big-ip — versions 21.0.0, 17.5.0, 17.1.0

Weakness classification (CWE)

CWE-420 — Unprotected Alternate Channel

References

f5sirt@f5.com (vendor-advisory, patch)

Frequently asked questions

What is CVE-2026-40435?: CVE-2026-40435 is a medium-severity vulnerability in F5 Big-ip, classified under Unprotected Alternate Channel. CVSS score: 5.3/10. Published 2026-05-13.
How severe is CVE-2026-40435?: Medium severity. CVSS v3 base score is 5.3 out of 10.