Vulnerability · NVD

CVE-2021-38507

MEDIUM 6.5 Published on 2021-12-08

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.

Attack vector : Network No privileges required

Show raw CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

EPSS 0.80% above median percentile 53.4%

Tracked apps referencing this CVE

For each app: the affected range, the fixing version, and where the tracked app stands today.

Mozilla Thunderbird Windows winget:Mozilla.Thunderbird

Affected <91.3.0 Fixed in 91.3.0 Latest tracked 153.0.2 patched

NVD references 4 distinct products for this CVE — only those tracked by Scout (mobile and desktop catalog apps) are listed above. Libraries, servers and out-of-scope products do not appear here. Full list on NVD ↗

Vulnerable CPE configurations (1)

Vendor	Product	Platform	Versions	CPE 2.3 URI
mozilla	thunderbird All platforms (wildcard)	All platforms (wildcard)	<91.3.0	cpe:2.3:a:mozilla:thunderbird::::::::

View on NVD ↗ Advisory · bugzilla.mozilla.org Advisory · www.mozilla.org