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MFSA2021-49 Firefox: Security Vulnerabilities fixed in Firefox ESR 91.3 (CVE-2021-38507)

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MFSA2021-49 Firefox: Security Vulnerabilities fixed in Firefox ESR 91.3 (CVE-2021-38507)

Severity
4
CVSS
(AV:N/AC:M/Au:N/C:N/I:P/A:N)
Published
11/02/2021
Created
11/04/2021
Added
11/03/2021
Modified
11/26/2024

Description

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.

Solution(s)

  • mozilla-firefox-esr-upgrade-91_3

References

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