UBUNTU-CVE-2021-38507

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UBUNTU-CVE-2021-38507

Summary:

Details: The Opportunistic Encryption feature of HTTP2 (RFC 8164) allows a connection to be transparently upgraded to TLS while retaining the visual properties of an HTTP connection, including being same-origin with unencrypted connections on port 80. However, if a second encrypted port on the same IP address (e.g. port 8443) did not opt-in to opportunistic encryption; a network attacker could forward a connection from the browser to port 443 to port 8443, causing the browser to treat the content of port 8443 as same-origin with HTTP. This was resolved by disabling the Opportunistic Encryption feature, which had low usage. This vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.

References: https://ubuntu.com/security/CVE-2021-38507, https://www.mozilla.org/en-US/security/advisories/mfsa2021-48/#CVE-2021-38507, https://www.mozilla.org/en-US/security/advisories/mfsa2021-49/#CVE-2021-38507, https://ubuntu.com/security/notices/USN-5131-1, https://ubuntu.com/security/notices/USN-5152-1, https://ubuntu.com/security/notices/USN-5248-1, https://www.cve.org/CVERecord?id=CVE-2021-38507