CVE-2021-38507 Security feature bypass in Firefox
Network attackers can bypass same-origin policies by redirecting HTTP/2 connections, causing browsers to treat unencrypted and encrypted content as same-origin.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2021-38507?
CVE-2021-38507 is a medium-severity vulnerability in Debian Debian Linux, published on 8 Dec 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-346
Which versions are affected by CVE-2021-38507?
It affects 4 products.
Products include Debian Debian Linux, Mozilla Firefox, Mozilla Firefox Esr, Mozilla Thunderbird.
How do I fix CVE-2021-38507?
Upgrade to a fixed version.
Is CVE-2021-38507 being exploited?
There is no known exploitation of CVE-2021-38507 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as DEBIAN-CVE-2021-38507, GHSA-mvf9-xj62-qhwc, UBUNTU-CVE-2021-38507.