CVE-2025-70515

Executive Summary

CVE-2025-70515 is a reflected cross-site scripting (XSS) vulnerability in the device log component of Fanvil x7a IP phones running firmware version 2.6.0.1182. Because the device log interface fails to sanitize or encode user-supplied data before reflecting it back to the browser, an attacker who lures a victim to a crafted request can execute arbitrary JavaScript in the context of the phone's web management UI. Impact is limited to the confidentiality and integrity of the affected phone session (CVSS is not assigned by the NVD), but successful exploitation can hijack an authenticated administrator session or perform actions on the device as the victim.

Technical Analysis

The vulnerability resides in the "device log component" of Fanvil x7a firmware 2.6.0.1182. Per the NVD description, that component "does not properly sanitize or encode reflected user supplied data." This is the textbook definition of reflected cross-site scripting (CWE-79): data supplied in an HTTP request is incorporated into an HTML response without output encoding, so any markup the attacker supplies is rendered as live HTML by the victim's browser.

The attack surface is the device log viewer exposed by the phone's embedded web server — a browser-accessible management interface that renders diagnostic/log output. Because the data flows reflected rather than stored, the vulnerable parameter is carried in a request the victim must issue (typically a crafted link the attacker sends to the administrator of the phone). The lack of sanitization or encoding means that a supplied string containing HTML tags will be interpreted as document structure rather than inert text; by extension, an injected HTML element with a script-bearing construct (for example a <script> element or an event-handler attribute) executes JavaScript in the origin of the management UI.

The failure mode is an output-encoding defect, not an authentication defect or memory-corruption issue. No information is provided in the CVE data that identifies specific parameter names, request paths, or handler functions, and none are inferred here. The relevant fact is the classes of data involved: the device log component takes user-supplied input and writes it into a response the browser interprets and renders. An important nuance of the NVD wording — "execute malicious JavaScript code on any target browser which renders the device log component" — implies the reflection is not confined to the requesting session; any browser that loads the affected log view with the injected input will execute the script.

The XSS executes in the origin of the phone's web interface rather than of an external site, so the trust boundary crossed is the phone's own management origin. Reaching the interface generally requires network access to the device's HTTP/HTTPS management port, which on an enterprise voice VLAN is frequently reachable from a compromised endpoint or from a malicious insider. The CVE data assigns no CVSS score and no vector (CVSS: N/A), and no CWE mapping is published — CWE-79 is the appropriate class mapping for a reflected XSS defect. No public PoC or exploit code is available.

Exploitation Scenarios

The following chain is described strictly at the vulnerability-class level, because the CVE data does not disclose specific endpoint, parameter, or function names. No public PoC exists; the chain is inferred from the reflected-XSS class.

1. Reconnaissance and target identification. The attacker identifies reachable Fanvil x7a devices — for example by scanning for the embedded web management interface using the Shodan-style fingerprints above, or by enumerating the voice VLAN. The attacker confirms the firmware version is 2.6.0.1182, the only version named in the advisory, and locates the device log view within the management UI.

2. Crafting the malicious link. The attacker constructs a URL that reaches the device log component and carries an injected HTML/JavaScript payload in the reflected input position. Because the component does not sanitize or encode the supplied value, the payload is written into the returned HTML. The exact parameter name and path are not disclosed in the CVE data and are not invented here.

3. Delivery and triggering. The payload is not delivered automatically — the attacker must cause a victim (typically an authenticated administrator of the phone or a user on the same management network) to open the crafted link or otherwise render the device log view. This is the user-interaction step intrinsic to reflected XSS. The NVD description notes the script runs in "any target browser which renders the device log component," meaning delivery is not limited to a single pre-existing session.

4. Execution and post-exploitation impact. The script executes in the origin of the Fanvil management UI. From that position the attacker can read what the browser exposes in that origin, act on the device through the victim's authenticated session (for example issue requests using the victim's context), and redirect or socially engineer the victim further. The scope of the impact is bounded by what the phone's management session can do — configuration retrieval or modification, depending on the victim's privilege level — and by the absence of a patch. Without a fix, the same crafted request can be re-delivered to each victim.

Impact Assessment

The NVD assigns no CVSS score or vector for this CVE, and no EPSS value has been published by FIRST.org, so quantitative risk scoring is unavailable. Class-level impact for reflected XSS in a device management UI is: partial confidentiality impact on session data, partial integrity impact on actions performable within the hijacked session, no direct availability impact, and increased scope because code executes in the origin of the affected device's interface rather than the attacker's site. The typical inferred vector (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N) reflects network reachability, low attack complexity, no privileges required, and required user interaction.

Affected systems are Fanvil x7a IP phones at firmware 2.6.0.1182. Blast radius within an enterprise is bounded by management-plane reachability: the vulnerability is only exploitable by an attacker who can reach the device's web interface and persuade a user to render the crafted log view. In environments where IP phones share a VLAN with user workstations, or where the management interface is exposed beyond the voice segment, the practical reachability — and therefore the exposure — increases. Voice is a high-availability service in many organizations; a compromised administrator session on a phone can yield configuration access to that device. No CISA KEV listing exists, and no in-the-wild exploitation has been reported, so the immediate threat is opportunistic rather than actively weaponized.

Detection Guidance

Because this CVE has no public PoC, the following detections are generalized for reflected XSS against an embedded device management UI and should be tuned to the actual request paths observed on the deployment.

Sigma Rule

title: Reflected XSS Attempt Against Fanvil x7a Device Log Component (CVE-2025-70515)
id: 4e1a9c2b-7d3f-4b6a-9c11-fanvilx7a0001
status: experimental
description: Detects HTTP requests containing script/HTML payload markers targeting the Fanvil x7a device log interface.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2025-70515
author: valtersit.com threat intelligence
date: 2025/01/01
logsource:
  category: webserver
  product: fanvil
detection:
  selection_method:
    cs-method:
      - 'GET'
      - 'POST'
  selection_payload:
    cs-uri-query|contains:
      - '<script'
      - '</script>'
      - 'javascript:'
      - 'onerror='
      - 'onload='
      - '<img'
      - '<svg'
      - 'alert('
  condition: selection_method and selection_payload
falsepositives:
  - Benign administrative testing against the log viewer
  - Security scanners that probe for XSS without intent to exploit
level: medium
tags:
  - attack.t1059.007
  - cve.2025.70515

YARA Rule

rule CVE_2025_70515_Fanvil_X7A_Reflected_XSS
{
    meta:
        description = "Detects reflected XSS payload markers targeting the Fanvil x7a device log component (CVE-2025-70515)"
        author = "valtersit.com threat intelligence"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-70515"
        date = "2025-01-01"
        severity = "medium"

    strings:
        $script_open  = "<script" ascii nocase
        $script_close = "</script>" ascii nocase
        $svg_onload   = "<svg" ascii nocase
        $img_onerror  = "<img" ascii nocase
        $js_scheme    = "javascript:" ascii nocase
        $onerror      = "onerror=" ascii nocase
        $onload       = "onload=" ascii nocase
        $alert        = "alert(" ascii nocase
        $doc_cookie   = "document.cookie" ascii nocase

    condition:
        (
            $script_open or $svg_onload or $img_onerror
        ) and 1 of (
            $script_close, $js_scheme, $onerror, $onload, $alert, $doc_cookie
        )
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2025-70515 Fanvil x7a Reflected XSS Attempt in Device Log"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"<script"; nocase; http.uri; content:"</script>"; nocase; http.uri; content:"javascript:"; nocase; http.uri; content:"onerror="; nocase; http.uri; content:"onload="; nocase; pcre:"/(%3C|<)\s*script|(onerror|onload)\s*=|javascript%3A|javascript:/iU"; classtype:web-application-attack; reference:cve,2025-70515; reference:url,nvd.nist.gov/vuln/detail/CVE-2025-70515; sid:2025705150; rev:1;)

Elastic Detection

sequence by source.ip with maxspan=30s
  [network where
     event.category == "network" and
     network.transport == "tcp" and
     network.direction == "outbound" and
     http.request.method in ("GET", "POST") and
     (
        url.query contains "<script" or
        url.query contains "</script>" or
        url.query contains "javascript:" or
        url.query contains "onerror=" or
        url.query contains "onload=" or
        url.query contains "alert("
     )
  ]

Splunk SPL Query

index=web OR index=proxy
| search (uri="*<script*" OR uri="*%3Cscript*" OR uri="*javascript:*" OR uri="*onerror=*" OR uri="*onload=*" OR uri="*alert(*" OR uri="*</script>*")
| rex field=uri "(?<payload>(<|%3C)script|javascript:|onerror=|onload=)"
| stats count values(uri) as requested_uris values(src_ip) as source_ips by dest_host, payload
| where count >= 1
| sort - count

Wazuh OSSEC Rule

<group name="fanvil,web,attack,">
  <rule id="2025701" level="10">
    <decoded_as>web-accesslog</decoded_as>
    <description>CVE-2025-70515 - Possible reflected XSS attempt targeting Fanvil x7a device log component</description>
    <match>|</match>
    <regex type="pcre2">(?i)(&lt;|<)\s*script|javascript%3A|javascript:|onerror\s*=|onload\s*=</regex>
    <group>cve_2025_70515,xss_attempt,</group>
  </rule>

  <rule id="2025702" level="12">
    <decoded_as>web-accesslog</decoded_as>
    <description>CVE-2025-70515 - XSS payload with document access attempt against Fanvil x7a device log</description>
    <regex type="pcre2">(?i)(document\.cookie|document\.location|XMLHttpRequest|fetch\()</regex>
    <group>cve_2025_70515,xss_exploitation,</group>
  </rule>
</group>

Note: the exact request paths and parameters for the device log component are not specified in the available CVE data, so detection rules target request content rather than named endpoints.

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source). No vendor fix version, workaround, or advisory patch reference was identified for this CVE, and Fanvil has not published a remediating firmware in the data reviewed.

1. Immediate mitigations:

   • Remove or restrict network reachability to the x7a management web interface. Place phones on a dedicated voice VLAN and firewall the management port so it is reachable only from a hardened administrative segment.
   • Do not expose the device web UI to untrusted networks or the internet.
   • Treat links/requests referencing the device log view as untrusted; avoid opening them from email or chat messages.
   • Where possible, disable remote/browser-based management on the affected devices until a fix is available.
   • Monitor web access logs for the XSS payload markers given in the detection section.

2. Patch/upgrade steps:

   • No patch is currently available (patch confidence 0/4). Track Fanvil's security advisory channel for the x7a product line and apply firmware newer than 2.6.0.1182 as soon as it is released and validated.
   • Inventory all x7a devices and record exact firmware versions so that the vulnerable population is known when a fix ships.

3. Long-term hardening:

   • Enforce a patch/patch-management process for VoIP endpoints, which are frequently treated as appliances rather than patchable software.
   • Segment voice, management, and user networks; apply least-privilege access to the device management plane.
   • Deploy browser-side mitigations (a modern browser, and where feasible a content security policy for the management origin if the vendor supports it) to reduce the impact of reflected script execution.
   • Require administrator re-authentication and short session lifetimes for device management consoles.

References

• NVD — CVE-2025-70515: https://nvd.nist.gov/vuln/detail/CVE-2025-70515
• CWE-79, Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'): https://cwe.mitre.org/data/definitions/79.html
• OWASP Cross Site Scripting Prevention Cheat Sheet: https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html
• MITRE ATT&CK T1059.007, Command and Scripting Interpreter: JavaScript: https://attack.mitre.org/techniques/T1059/007/
• CISA Known Exploited Vulnerabilities Catalog (CVE-2025-70515 not listed): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

No threat actor campaigns and no exploit-in-the-wild activity have been reported for this CVE; CISA KEV status is NO, no public PoC or exploit code is available, and no Nuclei template exists.