CVE-2026-40435
F5 Big-Ip Access Policy Manager 17.1.0 – 17.1.3
Raw vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/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:XSummary
CVE-2026-40435 is a medium-severity Unprotected Alternate Channel (CWE-420) vulnerability in F5 Big-Ip Access Policy Manager. Its CVSS base score is 6.9 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Fallback Channels (T1008); ranked at the 14th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SC-8 (Transmission Confidentiality and Integrity) and AC-4 (Information Flow Enforcement) — see the control section below for these in your framework.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-29973
Vulnerability Data
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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Transmission confidentiality and integrity requirements apply to all transmitted data, preventing weaker protection on secondary channels.
Information flow enforcement requires consistent authorization and control over every path, directly stopping unequal protection of alternate channels.
Boundary protection mandates monitoring and control at all external and key internal interfaces, eliminating unprotected alternate channels.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Protecting all data-in-transit directly mitigates unequal channel protection though the control addresses broader transit scenarios.
Network protection from unauthorized access inherently requires securing every channel, not just primaries.
Network monitoring can surface use of unprotected alternate channels but does not prevent the design flaw.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Access restrictions may cover primary paths but leave alternate channels unprotected unless explicitly extended.
Secure authentication applies to primary channels but does not ensure alternate channels receive the same strength.
Network security controls ensure all channels receive equivalent protection, directly addressing unprotected alternate channels.
Security of network services requires consistent protection across all service channels, mitigating alternate-channel weaknesses.
Network segregation can reduce exposure of alternate channels but does not guarantee equivalent protection levels.
Cryptography can protect alternate channels but does not address the policy of applying equal protection across channels.