CVE-2026-119425
OPNsense 26.1.6 through 26.7.7 Captive Portal Session Takeover via Forged ARP
- State
- Published
- Severity
- 5.3 Medium
- Published
- Oct 30, 2026
- Updated
- Oct 30, 2026
- Reserved
- Oct 30, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 5.3 Medium | CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N | VulnCheck |
| 3.1 | 5.4 Medium | CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N | VulnCheck |
Weaknesses
- CWE-290 Authentication Bypass by Spoofing
Affected Products
| Product | Versions |
|---|---|
coreopnsense |
|
References
- GitHub Security Advisory (GHSA-864r-q4j5-5mjq)vendor-advisory
- Incomplete fixpatch
- Incomplete fix (stable/26.7)patch
- https://github.com/opnsense/core/blob/26.7.7/src/opnsense/scripts/captiveportal/cp-background-process.py#L78technical-description
- https://abraxaslabs.tech/research/opnsense-captive-lastseen-roamthird-party-advisory
- https://github.com/opnsense/coreproduct
- VulnCheck Advisory: OPNsense 26.1.6 through 26.7.7 Captive Portal Session Takeover via Forged ARPthird-party-advisory
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