cbcvebase.
CVE-2021-38507
published 2021-12-08

CVE-2021-38507: The Opportunistic Encryption feature of HTTP2 (RFC 8164) allows a connection to be transparently upgraded to TLS while retaining the visual properties of an…

PriorityP430medium6.5CVSS 3.1
AVNACLPRNUIRSUCNIHAN
EPSS
0.80%
52.3th percentile
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

21 ranges
VendorProductVersion rangeFixed in
debiandebian_linux
debiandebian_linux
debiandebian_linux
debianfirefox< firefox 94.0-1 (sid)firefox 94.0-1 (sid)
debianfirefox-esr< firefox 94.0-1 (sid)firefox 94.0-1 (sid)
debianthunderbird< firefox 94.0-1 (sid)firefox 94.0-1 (sid)
mozillafirefox< 94.094.0
mozillafirefox
mozillafirefox>= 0 < 94.0+build3-0ubuntu0.18.04.194.0+build3-0ubuntu0.18.04.1
mozillafirefox>= 0 < 94.0+build3-0ubuntu0.20.04.194.0+build3-0ubuntu0.20.04.1
mozillafirefox>= unspecified < 9494
mozillafirefox_esr< 91.3.091.3.0
mozillafirefox_esr>= unspecified < 91.391.3
mozillathunderbird< 91.3.091.3.0
mozillathunderbird>= 0 < 1:91.4.1-1~deb11u11:91.4.1-1~deb11u1
mozillathunderbird>= 0 < 1:91.3.0-11:91.3.0-1
mozillathunderbird>= 0 < 1:91.3.0-11:91.3.0-1
mozillathunderbird>= 0 < 1:91.3.0-11:91.3.0-1
mozillathunderbird>= 0 < 1:91.5.0+build1-0ubuntu0.18.04.11:91.5.0+build1-0ubuntu0.18.04.1
mozillathunderbird>= 0 < 1:91.5.0+build1-0ubuntu0.20.04.11:91.5.0+build1-0ubuntu0.20.04.1
mozillathunderbird>= unspecified < 91.391.3

CVSS provenance

nvdv3.16.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
nvdv2.04.3MEDIUMAV:N/AC:M/Au:N/C:N/I:P/A:N
osv10.0CRITICAL
vendor_ubuntu10.0CRITICAL
vendor_debian6.5MEDIUM
vendor_redhat6.5MEDIUM
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