Attacker Value
Unknown
(0 users assessed)
Exploitability
Unknown
(0 users assessed)
User Interaction
Required
Privileges Required
None
Attack Vector
Network
0

CVE-2021-38507

Disclosure Date: December 08, 2021 •
CVE-2021-38507 CVSS v3 Base Score: 6.5
Add MITRE ATT&CK tactics and techniques that apply to this CVE.

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.

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CVSS V3 Severity and Metrics
Base Score:
6.5 Medium
Impact Score:
3.6
Exploitability Score:
2.8
Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
Attack Vector (AV):
Network
Attack Complexity (AC):
Low
Privileges Required (PR):
None
User Interaction (UI):
Required
Scope (S):
Unchanged
Confidentiality (C):
None
Integrity (I):
High
Availability (A):
None

General Information

Offensive Application
Unknown
Utility Class
Unknown
Ports
Unknown
OS
Unknown
Vulnerable Versions
Firefox 94
Thunderbird 91.3
Firefox ESR 91.3
Prerequisites
Unknown
Discovered By
Unknown
PoC Author
Unknown
Metasploit Module
Unknown
Reporter
Unknown

Vendors

  • debian,
  • mozilla

Products

  • debian linux 10.0,
  • debian linux 11.0,
  • debian linux 9.0,
  • firefox,
  • firefox esr,
  • thunderbird
Technical Analysis