Vulnerability in opnsense core

[ Description ]Official description

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.

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ References ]References

• abraxaslabs.tech/research/opnsense-captive-lastseen-roam
• github.com/opnsense/core
• github.com/opnsense/core/blob/26.7.7/src/opnsense/scripts/captiveportal/cp-background-p…
• github.com/opnsense/core/commit/32dc2a3e52eefef5251077f315a0f3243eedb834
• github.com/opnsense/core/commit/f46836d0c3d14e26d79214009bfbfa9a1eecab55
• github.com/opnsense/core/security/advisories/GHSA-864r-q4j5-5mjq
• www.vulncheck.com/advisories/opnsense-26.1.6-through-26.7.7-captive-portal-session-take…