OPNsense core 26.1.6 through 26.7.7 contains an authentication bypass vulnerability in the captive portal roaming feature that lets unauthenticated attackers hijack authorized client sessions by spoofing unauthenticated MAC-to-IP observations. Attackers on the same Layer-2 segment can send forged gratuitous ARP replies binding their IP to a victim's MAC, gaining portal access with traffic attributed to the victim.
Fix
Patch, vendor advisory and mitigation references on NVD 2
- https://github.com/opnsense/core/commit/f46836d0c3d14e26d79214009bfbfa9a1eecab55 patch
- https://github.com/opnsense/core/commit/32dc2a3e52eefef5251077f315a0f3243eedb834 patch
Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.
Change history 1
- First seenCVSS 5.3 · opnsenseNVD modified 2026-10-30 11:30
Affected (CPE criteria) 0
NVD has not attached CPE configurations yet.
References 7
- https://github.com/opnsense/core/security/advisories/GHSA-864r-q4j5-5mjq vendor-advisory
- https://github.com/opnsense/core/commit/f46836d0c3d14e26d79214009bfbfa9a1eecab55 patch
- https://github.com/opnsense/core/commit/32dc2a3e52eefef5251077f315a0f3243eedb834 patch
- https://github.com/opnsense/core/blob/26.7.7/src/opnsense/scripts/captiveportal/cp-background-process.py#L78 technical-description
- https://abraxaslabs.tech/research/opnsense-captive-lastseen-roam third-party-advisory
- https://github.com/opnsense/core product
- https://www.vulncheck.com/advisories/opnsense-26.1.6-through-26.7.7-captive-portal-session-takeover-via-forged-arp third-party-advisory