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.
History

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cve-icon MITRE Information

Status: PUBLISHED

Assigner: mozilla

Published: 2021-12-08T21:21:41

Updated: 2022-08-10T05:11:20

Reserved: 2021-08-10T00:00:00


Link: CVE-2021-38507

JSON object: View

cve-icon NVD Information

Status : Analyzed

Published: 2021-12-08T22:15:08.947

Modified: 2022-12-09T15:54:38.630


Link: CVE-2021-38507

JSON object: View

cve-icon Redhat Information

No data.

CWE