Vulnerability CVE-2021-38507


Published: 2021-12-08   Modified: 2021-12-09

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.

Type:

CWE-346

(Origin Validation Error)

CVSS2 => (AV:N/AC:M/Au:N/C:N/I:P/A:N)

CVSS Base Score
Impact Subscore
Exploitability Subscore
4.3/10
2.9/10
8.6/10
Exploit range
Attack complexity
Authentication
Remote
Medium
No required
Confidentiality impact
Integrity impact
Availability impact
None
Partial
None
Affected software
Mozilla -> Firefox 
Mozilla -> Firefox esr 
Mozilla -> Thunderbird 

 References:
https://www.mozilla.org/security/advisories/mfsa2021-50/
https://bugzilla.mozilla.org/show_bug.cgi?id=1730935
https://www.mozilla.org/security/advisories/mfsa2021-49/
https://www.mozilla.org/security/advisories/mfsa2021-48/

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