CVE-2021-38507
Expert Analysis
Professional remediation guidance
Get tailored security recommendations from our analyst team for CVE-2021-38507. We'll provide specific mitigation strategies based on your environment and risk profile.
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.
Available Exploits
Related News
Affected Products
Affected Versions:
Affected Versions:
Affected Versions:
GitHub Security Advisories
Community-driven vulnerability intelligence from GitHub
Advisory Details
CVSS Scoring
CVSS Score
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
References
Advisory provided by GitHub Security Advisory Database. Published: December 9, 2021, Modified: March 17, 2022