advisories/nc-sa-2020-038.php


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    <h1>Security Advisory</h1>
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        <h2>Message Authentication Codes calculated by the Default Encryption Module allow an attacker to silently overwrite blocks in a file (NC-SA-2020-038)</h2>
        <p>26th August 2020</p>
        <p>Risk level: <strong>Low</strong></p>
        <p>CVSS v3 Base Score: 1.8 (<a href="https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:L/AC:H/PR:H/UI:R/S:U/C:N/I:L/A:N">AV:L/AC:H/PR:H/UI:R/S:U/C:N/I:L/A:N</a>)</p>
        <p>CWE: <a href="https://cwe.mitre.org/data/definitions/657.html">Violation of Secure Design Principles (CWE-657)</a></p>
        <p>HackerOne report: <a href="https://hackerone.com/reports/661051">661051</a></p>
        <h3>Description</h3>
        <p>A wrong generation of the passphrase for the encrypted block in Nextcloud Server 19.0.1 allowed an attacker to overwrite blocks in a file.</p>
        <h3>Affected Software</h3>
        <ul>
            <li>Nextcloud Server &lt; <strong>19.0.2</strong> (CVE-2020-8133)</li>
<li>Nextcloud Server &lt; <strong>18.0.8</strong> (CVE-2020-8133)</li>
<li>Nextcloud Server &lt; <strong>17.0.10</strong> (CVE-2020-8133)</li>

        </ul>
        <h3>Action Taken</h3>
        <p>The error has been fixed.</p>
        <h3>Resolution</h3>
        <p>It is recommended that the Nextcloud Server is upgraded to 19.0.2.</p>
        <h3>Acknowledgements</h3>
        <p>The Nextcloud team thanks the following people for their research and responsible disclosure of the above advisory:</p>
        <ul>
            <li><a href="https://www.syseleven.de/" target="_blank" rel="noreferrer">Kevin "Kenny" Niehage - SysEleven GmbH (kenny@syseleven.de) - Vulnerability discovery and disclosure.</a></li>
        </ul>
        <br/>
        <small style="color:grey">This advisory is licensed <a href="https://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA 4.0</a>.</small>
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