CVE-2021-38507 — Mozilla / Firefox

Description (CNA)

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.

Affected (CNA)

Vendor / product	Versions
Mozilla / Firefox	affected unspecified before 94
Mozilla / Thunderbird	affected unspecified before 91.3
Mozilla / Firefox ESR	affected unspecified before 91.3

CWE

No CWE identifiers supplied.

References

ADP enrichment

CVE

No English description supplied.