CVE-2026-96258: Auktion NG Auktionssoftware XSS Vulnerability

CVE-2026-96258 Overview

CVE-2026-96258 is a reflected cross-site scripting (XSS) vulnerability in onSite internet GmbH Auktion NG Auktionssoftware versions up to 20260722. The flaw resides in the public password reset endpoint at /forgotpasswd.html, where the email parameter is not properly sanitized before being reflected in the response. An unauthenticated remote attacker can craft a malicious URL that, when visited by a target user, executes attacker-controlled script in the victim's browser context. The vendor was contacted before public disclosure but did not respond, and the exploit details have been published.

Critical Impact
Attackers can execute arbitrary JavaScript in a victim's browser session by luring them to a crafted password reset URL, enabling session theft, phishing overlays, or account compromise workflows.

Affected Products

onSite internet GmbH Auktion NG Auktionssoftware versions up to 20260722
Component: Public Password Reset Endpoint (/forgotpasswd.html)
Affected parameter: email

Discovery Timeline

2026-09-23 - CVE-2026-96258 published to the National Vulnerability Database (NVD)
2026-09-23 - Last updated in NVD database

Technical Details for CVE-2026-96258

Vulnerability Analysis

The vulnerability is a reflected cross-site scripting issue classified under CWE-79: Improper Neutralization of Input During Web Page Generation. The /forgotpasswd.html endpoint accepts an email argument from the client and returns it in the rendered HTML response without encoding characters such as <, >, or ". This allows an attacker to inject HTML and JavaScript payloads that execute in the context of the vulnerable application's origin.

Because the affected endpoint is a public password reset workflow, it does not require authentication or prior account access. Successful exploitation depends on user interaction, typically clicking a crafted link delivered through phishing or social engineering channels.

Root Cause

The root cause is missing output encoding of the email request parameter before it is reflected into the HTML response body of the password reset page. Without contextual encoding, browser-parsed markup and script tags supplied by the attacker are treated as trusted content originating from the application.

Attack Vector

The attack is carried out remotely over the network. An attacker constructs a URL targeting /forgotpasswd.html with a malicious payload in the email query parameter and delivers it to a victim. When the victim loads the URL, the injected script executes under the origin of the Auktion NG application, giving the attacker access to cookies, form data, and any authenticated session state associated with that origin.

No verified proof-of-concept code is available in the referenced sources. Refer to the VulDB CVE Record and the GitHub Issue Discussion for additional context.

Detection Methods for CVE-2026-96258

Indicators of Compromise

Requests to /forgotpasswd.html containing HTML tags, script fragments, or URL-encoded angle brackets in the email parameter (for example %3Cscript%3E, onerror=, javascript:).
HTTP referrers from external domains pointing users to the password reset endpoint with unusual query strings.
Web server access logs showing repeated password reset requests with anomalously long or encoded email values.

Detection Strategies

Deploy web application firewall (WAF) rules that inspect the email parameter on /forgotpasswd.html for XSS signatures and reject non-email-format input.
Correlate outbound browser telemetry with inbound reset URL clicks to identify users who executed injected scripts.
Perform static and dynamic testing of the password reset flow to confirm output encoding on any reflected user input.

Monitoring Recommendations

Enable Content Security Policy (CSP) reporting to capture blocked inline script executions originating from the reset page.
Alert on HTTP 200 responses to /forgotpasswd.html whose response bodies contain reflected <script> or event-handler attributes.
Monitor authentication logs for session anomalies immediately following password reset traffic from unusual referrers.

How to Mitigate CVE-2026-96258

Immediate Actions Required

Restrict or disable public access to /forgotpasswd.html at the reverse proxy or WAF until a vendor patch is available.
Apply input validation that rejects any email parameter value not matching a strict email address grammar.
Notify users of the phishing risk associated with crafted password reset links and encourage them to initiate resets only from the official application UI.

Patch Information

No vendor patch or advisory has been published. According to the disclosure, the vendor did not respond to early contact attempts. Organizations running Auktion NG Auktionssoftware versions up to 20260722 should track the VulDB Vulnerability Information page for updates and consider compensating controls in the interim.

Workarounds

Deploy a WAF rule that blocks or sanitizes requests to /forgotpasswd.html where the email parameter contains <, >, ", ', or javascript:.
Enforce a strict Content Security Policy that disallows inline scripts and untrusted script sources on the password reset page.
Set the HttpOnly and Secure flags on session cookies to reduce the impact of successful script execution.
If feasible, front the application with a reverse proxy that rewrites or strips reflected content in responses from the reset endpoint.

bash

# Example ModSecurity rule to block XSS payloads on the password reset endpoint
SecRule REQUEST_URI "@beginsWith /forgotpasswd.html" \
    "phase:2,chain,deny,status:403,id:1096258,msg:'Blocked XSS attempt on Auktion NG password reset'"
    SecRule ARGS:email "@rx (?i)(<script|onerror=|onload=|javascript:|<img|<svg)" "t:none,t:urlDecodeUni"