| CVE-2021-38507 | Date: (C)2021-12-10 (M)2024-03-27 |
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.
CVSS Score and Metrics +CVSS Score and Metrics -| CVSS V3 Severity: | CVSS V2 Severity: |
| CVSS Score : 6.5 | CVSS Score : 4.3 |
| Exploit Score: 2.8 | Exploit Score: 8.6 |
| Impact Score: 3.6 | Impact Score: 2.9 |
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| CVSS V3 Metrics: | CVSS V2 Metrics: |
| Attack Vector: NETWORK | Access Vector: NETWORK |
| Attack Complexity: LOW | Access Complexity: MEDIUM |
| Privileges Required: NONE | Authentication: NONE |
| User Interaction: REQUIRED | Confidentiality: NONE |
| Scope: UNCHANGED | Integrity: PARTIAL |
| Confidentiality: NONE | Availability: NONE |
| Integrity: HIGH | |
| Availability: NONE | |
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