CVE-2025-25264: Cross-Site Scripting (XSS) Vulnerability

CVE-2025-25264 Overview

CVE-2025-25264 is an information disclosure vulnerability caused by an overly permissive Cross-Origin Resource Sharing (CORS) policy. An unauthenticated remote attacker can craft a website containing malicious JavaScript and trick an administrator into visiting it. When the admin loads the page, the attacker-controlled script can issue cross-origin requests to the vulnerable application and read arbitrary files from the underlying file system. The issue is classified under [CWE-942] (Permissive Cross-domain Policy with Untrusted Domains) and was published to the National Vulnerability Database on 2025-06-16.

Critical Impact
Successful exploitation allows an unauthenticated attacker to exfiltrate arbitrary files from the target file system by luring an administrator to a malicious page.

Affected Products

Product details are listed in CERTVDE Advisory VDE-2025-018
No CPE entries were published in NVD at the time of writing
Refer to the vendor advisory for exact affected versions and firmware builds

Discovery Timeline

2025-06-16 - CVE-2025-25264 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-25264

Vulnerability Analysis

The vulnerability stems from a CORS configuration that reflects or wildcards the Access-Control-Allow-Origin header while also permitting credentialed requests. This configuration allows any origin to issue authenticated cross-origin requests against the application and read the responses. The condition maps to [CWE-942], where the server trusts arbitrary external domains for cross-origin interactions.

Exploitation requires user interaction, but no privileges on the attacker side. An administrator with an active session is the primary target because their credentials or session cookies are needed to retrieve protected resources. Once the admin browses the attacker-controlled page, JavaScript on that page silently drives the browser to request files through the application's exposed endpoints.

The EPSS probability for CVE-2025-25264 is 0.386%, reflecting a low but non-trivial likelihood of exploitation attempts in the near term.

Root Cause

The root cause is a permissive CORS policy that accepts requests from untrusted origins. Rather than restricting Access-Control-Allow-Origin to a fixed allowlist of trusted domains, the application echoes the request Origin header or returns a wildcard while permitting credentials. The result is that any external site can read authenticated responses from the application.

Attack Vector

The attack is network-based and requires the administrator to visit an attacker-controlled URL. The malicious page issues fetch or XMLHttpRequest calls to file-serving endpoints of the vulnerable application. Because the CORS policy allows the response to be read cross-origin with credentials, JavaScript on the attacker page receives file contents and forwards them to an external server. The vulnerability affects confidentiality only; integrity and availability are not directly impacted.

No verified proof-of-concept code is publicly available. See the CERTVDE Advisory VDE-2025-018 for further technical details.

Detection Methods for CVE-2025-25264

Indicators of Compromise

Outbound HTTP requests from administrator browsers to unfamiliar external domains shortly before large internal file reads.
HTTP responses from the vulnerable application containing Access-Control-Allow-Origin values that reflect arbitrary request origins.
Unexpected cross-origin fetch or XMLHttpRequest traffic in browser telemetry targeting internal management URLs.

Detection Strategies

Inspect application response headers and flag any Access-Control-Allow-Origin value that is not from a fixed allowlist, especially when combined with Access-Control-Allow-Credentials: true.
Correlate administrator web browsing telemetry with subsequent requests to the vulnerable application from the same session.
Alert on file-read endpoints returning content when the request Referer or Origin is external to the trusted management domain.

Monitoring Recommendations

Ingest web proxy and endpoint browser logs into a centralized data lake for cross-origin request analysis.
Monitor administrator workstations for phishing pages and drive-by JavaScript execution using EDR web-content telemetry.
Track configuration drift on the affected application to detect any change that reintroduces a permissive CORS policy.

How to Mitigate CVE-2025-25264

Immediate Actions Required

Apply the vendor update referenced in CERTVDE Advisory VDE-2025-018 as soon as it is available for your deployment.
Restrict administrative access to the application to trusted management networks only.
Instruct administrators to use a dedicated browser profile for management interfaces and avoid general web browsing in that profile.

Patch Information

Consult the CERTVDE Advisory VDE-2025-018 for the authoritative list of fixed versions and remediation steps. The advisory is the source of record referenced by the NVD entry for CVE-2025-25264.

Workarounds

Place the affected application behind a reverse proxy that enforces a strict Access-Control-Allow-Origin allowlist and strips reflected origin headers.
Disable Access-Control-Allow-Credentials on endpoints that do not require authenticated cross-origin access.
Require administrators to log out of the management interface immediately after use to reduce the window in which a malicious page can abuse an active session.

bash

# Example reverse proxy CORS hardening (nginx)
map $http_origin $cors_ok {
    default                       "";
    "https://admin.example.internal" $http_origin;
}

server {
    location / {
        add_header Access-Control-Allow-Origin      $cors_ok always;
        add_header Access-Control-Allow-Credentials true    always;
        add_header Vary                              Origin  always;

        if ($cors_ok = "") {
            return 403;
        }

        proxy_pass http://backend;
    }
}