MediumCVE-2026-119425

    OPNsense 26.1.6 through 26.7.7 Captive Portal Session Takeover via Forged ARP (CVE-2026-119425)

    Published Last modified Sources: CVE.org

    What is affected, what to do

    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.

    The available sources name no fixed version. Check the vendor guidance in the references below.

    Affected
    • Opnsense Core lte 26.1.6..26.7.7

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    5.4

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    5.4

    CVSS v3

    Severity Medium on the scale from 0 to 10.

    Source: CVE.org

    —

    EPSS score

    No value is available for this vulnerability.

    Show all metrics
    Severity
    Medium
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    57.00 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    5.4 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    5.4
    CVSS v4

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    5.3
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-290

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    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.

    Source: NVD (NIST), cvelistv5

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    opnsensecore
    • 26.1.6 – ≤ 26.7.7
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-290Authentication Bypass by Spoofing

      Base

      This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.

      Entry at MITRE CWE-290

    References & sources

    • abraxaslabs.techresearch/opnsense-captive-lastseen-roamThird-party advisory
    • github.comopnsense/coreProduct
    • github.comopnsense/core/blob/26.7.7/src/opnsense/scripts/captiveportal/cp…Technical description
    • github.comIncomplete fix (stable/26.7)Patch
    • github.comIncomplete fixPatch
    • github.comGitHub Security Advisory (GHSA-864r-q4j5-5mjq)Vendor advisory
    • vulncheck.comVulnCheck Advisory: OPNsense 26.1.6 through 26.7.7 Captive Portal Session Takeover via Forged ARPThird-party advisory

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-119425","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-30T15:20:58.656589Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    2. ReceivedVulnCheck

      CVSS V4.0: AV:A/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

      CVSS V3.1: AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

      Weakness type: CWE-290

      Description added or changed

      Show 12 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      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.
      CVSSadded
      —
      AV:A/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/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:X
      CVSSadded
      —
      AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
      Weakness type (CWE)added
      —
      CWE-290
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/119xxx/CVE-2026-119425.json">CVE-2026-119425</a>
      Referenceadded
      —
      https://abraxaslabs.tech/research/opnsense-captive-lastseen-roam
      Referenceadded
      —
      https://github.com/opnsense/core
      Referenceadded
      —
      https://github.com/opnsense/core/blob/26.7.7/src/opnsense/scripts/captiveportal/cp-background-process.py#L78
      Referenceadded
      —
      https://github.com/opnsense/core/commit/32dc2a3e52eefef5251077f315a0f3243eedb834
      Referenceadded
      —
      https://github.com/opnsense/core/commit/f46836d0c3d14e26d79214009bfbfa9a1eecab55
      Referenceadded
      —
      https://github.com/opnsense/core/security/advisories/GHSA-864r-q4j5-5mjq
      Referenceadded
      —
      https://www.vulncheck.com/advisories/opnsense-26.1.6-through-26.7.7-captive-portal-session-takeover-via-forged-arp

      Source identifier: disclosure@vulncheck.com

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